As a classic example see this node.

Well, I frontpaged that node. Why? Because the issue struck me. The anonymous monk (who gets no XP out of it, BTW :) had simply stumbled across some really weird behaviour of Perl, and IMO, it deserves attention.

In general, I tend to ++ questions that I consider good questions — I frontpage very good questions. This is, IMO, a good question. I think many people respond in that manner. BTW the rep of that node was already at 15 at the time I frontpaged it. So you're not correct that all of its rep comes from it having been frontpaged.