One issue I've seen come up a few times deals with a sense of scale in space. People's instincts on what can and cannot be done are often off by not just an order of magnitude, but an order of magnitude number of orders of magnitude! The same set of numbers tend to come up for describing just how big a project is, and that tends to get accepted as the answer, and we all move on.
I've heard at least one call to be able to just close these questions, but I'm not quite a fan of this. Just because the answer is "you weren't even close" doesn't make the question devoid of value (consider Lethal Neutrinos, one of the more epic order of magnitude problems I've ever seen). Besides, sometimes its just plain fun to see someone crunch the math and show just how small our measly humanity actually is! ("Give me a long enough lever and I will move the world" is really amusing if you ever try to crunch the numbers)
It does, however, make sense to do something with this class of problem. They're easy to spot. Just look for the answers using scientific notation with ridiculous exponents. If people keep coming in with these issues, is there something we can do to make the existing answers more useful, or easier to find?
Personally, I'm pondering the idea of retroactively tagging questions with a tag devoted to sense-of-scale-in-space, and in the answer pointing future question askers to look for that tag. I just don't know if that's a feasible approach or not... and I don't think my 5-word-long tag suggestion will fly.