We're not responsible for anyone keeping their jobs. I can think of one person in particular who falls into the category you mention (and we've both dealt with him).
My approach is this - if they've asked a question that might be beneficial to others, I'll try to formulate an answer regardless of how many similar questions they've asked. If the question is poor, I'll vote to close/flag/downvote it and move on.
At some point they get called out - comments are left that they're not accepting answers or providing feedback/clarification, and if you see enough of them to notice the name keeps popping up, odds are others do too. Questions start getting downvoted or simply not responded to. If you've noticed a problem, you're not obligated to answer anyone's questions. To me, there are no ethics invovled on your part unless you're knowingly decieving a third party. That's all the asker, be it cheating on homework or getting someone to teach them how to do their job (which they should have already known how to do - sometimes you do get new things you have to figure out how to do).
This is also a similar situation to RTFM questions. I really don't know why I see some of those questions get upvotes, and if I see a number of them from the same person I mention it. I've seen other community members moderate in a similar fashion (comments to the effect of what have you tried, did you look at the help, this site isn't really for that kind of thing, etc.) with varying degrees of tact. This is admittedly one of the things I sometimes struggle with, because RTFM seems so much more succinct and appropriate in some cases. :)
As for statistics, research, and methods... One thing you might want to keep in mind is that researchers don't always know GIS, and GIS users don't always know research fields. They may know the method to use, but not how to apply it spatially or with specific GIS software, or they may know what tools they have available but not which is best for a specific application. This applies even moreso to students. As a "GIS Guy", I look for how to solve a problem or apply a field solution in GIS. I don't know anything about the math involved or the formula itself, but if I understand the concepts I might be able to figure out an implementation - and learn something about a new field along the way.