Good point and I would point you to Robert's answer.
We've just expanded the on-topic page, with areas that were initially vague and unclear as to whether they were on topic or not, and which, over time, became clear that they should be on-topic. The initial proposal of the expansion was illustrated here, Game plan, and the final update was posted here, On-topic has been updated - finally!.
So, if your questions are on that (new, expanded) list then yes, they are on-topic. Otherwise, if they get posted they may get close votes, but then again people might find the question useful and run with it. It's up to the community really.
Sorry, if this answer is a bit vague and I can't be more specific (at the moment).
However, IMHO, I think that the site is intended to be more about the mechanics of 3D printing and getting something printed, rather than what you can do with 3D printed objects, as the latter is a extremely broad area, unbounded even. But others may have a more broader, and more accommodating, view.