I think there's a fine line between what is a list question with scope, and what is a list question where there can literally be an endless number of answers. I'll try to demonstrate this with a few examples.
For any of the questions listed below and their evaluation of how good a question it is, I request OPs not to take it a personal attack. These are simply my personal opinion on what I think is a good question or not. Other moderators or users may feel differently.
Antarctica - way to visit is GOOD: Okay, so this question straight up asks a list - on the surface. But how many ways, realistically, are there for a tourist to visit Antarctica? Not more than a handful. So there's still a way of determining one right answer, i.e., the one which lists the handful of realistic options tourists have.
Day trips from London is OKAY: Seemingly, a list question...but it can still have a right answer. It's asking for places OF INTEREST (nobody's going to be in London for a few days and go to Crawley or Farncombe for tourism) within a day's reach and back to London (the 'and back' part is important because otherwise that would through up a large part of the English Midlands too).
Good gelato places in Rome is BAD: What is 'good' gelato? There are literally dozens of gelato shops in Rome. So which one do you pick as the right answer?
Tipping wait staff in Europe is OKAY: A good canonical answer to this question will either list to a resource which answers the question or gives a list itself of what expected tips are - while the list could be large, it is still a FINITE and DEFINED list (all European countries). I say this one is 'okay' because it sort of got out of hand with people adding single line answers for each country.
Tips and tricks to get flight upgrades is GOOD: First up, this is well-worded, in that it doesn't ask for the 'best' tips to get an upgrade. But EVEN IF it did, it may still be answered objectively because the outcome is quantifiable (you either get an upgrade or not). A good canonical answer would list all possible tricks, but even if not and there are separate answers - how many techniques can you realistically expect? A dozen? And for each answer, there's a very objective measure of whether that tip works or not, i.e., is it successful in getting an upgrade.
Where can I see the Olympic Flame is GOOD: You could say this is a list question. You could end up getting one-line answers. "London!" "Birmingham!" But the point to note here is that even if it's hundreds of cities, it is still a FINITE and DEFINED subset. A good answer will list to an authoritative resource.
Must-see places in Goa is OKAY: The OP has done a poor job here of describing what he wants or not here, in fact, this was a question I considered shutting down but it has one crucial detail that works excellently in limiting scope: the OP only has one day free for exploring during a fifteen day business trip. So while in a sense it is somewhat subjective, it is limited in scope and the time restriction can help make a restricted list. The list of places of interest in a city could be huge, but if you factor in restrictions then a reasonable subset can be defined. You don't tell someone going to Paris for one day to not visit the Eiffel Tower.
List of free accommodation resources is a LEGACY QUESTION: Sometimes, questions come along that are useful (see European bike rentals) which may not have a right answer, so these were turned into 'community wikis'. Again, the criteria for this was that these need to be fact-based, rather than, say, 'List of restaurants in New York'. I suspect BOTH of those community wikis would have been closed if asked now, as we as community have refined the scope of Travel.SE. We simply haven't gone around retroactively locking old posts unless a specific issue crops up.
4 days in Paris is GOOD: This is another example of a question that is seemingly a list question but where the OP has defined parameters which limit scope and make it answerable:
- A budget of 200 euros, a tight budget, especially for a city like Paris
- He already has a wishlist of places he wants to see.
- A very specific timeframe (Friday noon to Monday evening). Maybe the places he wants to see are closed on the weekend?
In my opinion this is NOT an open-ended question, not completely. It gives a few parameters and then asks "Is this feasible?". The answer could then objectively be answer as "Yes" or "Yes...but it's going to cost you X amount more to fit in all places to want to see because you need to get faster trains" or whatever. Just an example of what the answers could be.
So I hope you see a pattern here. Due to the very nature of travelling, a LOT of questions could be considered 'list' questions. But what sets a good question apart from a bad question is that a good question has limited scope and some level of objectively measuring how good an answer is (for upgrade tricks, it depends on whether you get the upgrade; for haggling, what method gets you the best bargains is again a quantifiable measure).
I think this whole discussion started off because one particular question - What are the most unusual methods of transport? - got close-voted by community+moderator (VMAtm), reopened by community votes, and then closed again by me. Now, because I went against a community reopen vote I feel I should justify this: (I hope OP and other people involved see this as constructive criticism, not a personal attack)
- It is too subjective: What is 'unusual'? (The original wording was 'crazy'.) To me, travelling on camelback if I go to Rajasthan is not a novelty, for many Western travellers it is. Dog sleds in Alaska are commonplace, but is it an 'unusual' mode of transport since it's used in so few places? Or, if you consider dog sleds in Alaska commonplace, then would they be 'unusual' in the Himalayas, where they aren't typically used? As you can see, there isn't even a slight measure of objectivity.
- It is asking for a list, but no finite or defined list can exist because it's too subjective: As we have seen from examples earlier, even if a question asks for a list, it can be excellent question if the scope is limited or the list is defined (even if the list is large) and finite.
I think one of the best things that is coming out of the recent uptick in visitors on Travel.SE is that we now have a more engaged users who are increasingly doing a lot of community cleanup and policing work - edits, tagging, close or reopen votes. Earlier, it used to be just the mods who used to close questions that are somehow not suitable, for whatever reason, but now I often login to find questions I'd have closed or reopened already done so by the community. That's a good thing!
The problem with a things like what's a good list question or not is hard to pin down and codify for the FAQ, but I think given the issues raised in this meta discussion this is something we should look into. As a moderator, and a member of this Q&A site's community, I want to say that whenever I vote on closing questions (and I'm aware that statistically I'm the most active mod on that count) it's not 'random lunacy' but a thought-out decision on what can realistically be useful question with useful answers.
As always, all the tools for discussing are there. Use the reopen votes! Leave comments! Bring it up in chat! Flag it for moderator attention! Flagging is an important tool because sometimes, questions just slip past the moderators and we don't see it. Something that should be closed, doesn't; or an edited question doesn't get re-opened. And then we start off this whole exercise of "But you allowed that question! You should allow mine!" All the mods are doing this on a volunteer-basis, so it's not our full-time job to curate what goes on here. You can help by using your own community votes, edits, and judicious use of moderator tools to make this Q&A site better.
UPDATE 1: Further useful information from another StackExchange moderator (emphasis mine):
I'm starting to get really tired of seeing these "list question"
discussions come up... "List question" covers a lot of
not-very-related question types, and usually ends up confusing someone
who sees the discussion and thinks, "But what if the answer to my
question just happens to be... a list?"
There is some very specific guidance in the FAQ on every site...
The first three of those tend to result in lists. But... that's more
of a symptom of an underlying problem, aptly noted by Gilles in his
answer: these are "questions" that don't really have answers.
Stop fixating on lists. Avoid questions that aren't really questions.