In general (on all SE sites) I find that it's sometimes just plain difficult to word everything as a question and--even when it can be done--the title gets much wordier than a simple statement.
But that's just a preference. I can't say it's universally better one way or the other.
Random commentary on the first 5 titles currently out there:
Is the folder structure dying?
+1 for formatting as a question. It's enticing...slightly controversial. I think it being formatted as a question is a selling point for this one.
Jump from print into UX
+1 for a simple statement. It's not a question, but we can probably assume what the question(s) will be related to it. To word it as a question seems to just add superfluous words: How can I jump from print design into UX design? Not bad, just wordier.
Is it a good idea to redirect expected page name misspellings/typos for critical web pages?
+1 for question format. It's long, but seems appropriate for the specificity of the situation.
How can I pictorially show an option is unavailable for a time?
See previous. Seems to work well.
Using 2 tabs on a page: one for filter, and one for content?
Could this one be rewritten as a better question? Perhaps, but if you dive into the actual question, it seems that this is one of those "there's a question here, but that's actually part of the question: What question do I need to be asking?" Maybe this would have been better as a statement: Dealing with complex tabs and filter arrangement.
So, in summary: Uh, my conclusion is that, uh...I could go either way. It just seems that some question titles work best as questions, but some others are fine left as statements or fragments.
One size doesn't seem to fit all when it comes to question titles.