Brahms' music is rich and interesting, but not easily accessible to a layman. Justin Bieber's is not very interesting, but he gets downloaded from iTunes a lot.
In the last week or two, there have been a lot more questions at the advanced and research levels, and a number of professional physicists have been answering them. I almost never vote on these questions and their answers because I can't distinguish good from bad. It seems to be a rough general trend that the more advanced the question, the less voting there will be.
This might be construed as a disincentive to post research-level questions and answers as compared to more broadly-accessible ones. Someone who provides a lot of helpful, interesting answers to questions in their field might still wind up with low site reputation, especially compared to the high effort they put into answering technical questions. (I'm personally the opposite of this - I answer mostly basic-level questions and don't have a field.)
I would guess that if you ask most individual users, they would say that this isn't a problem for them because they don't care about reputation, except maybe to have enough to get full participation privileges. (That's what I would say, if you asked me.) However, as a whole, the behavior of users of StackExchange must be affected somewhat by reputation, or it wouldn't be recorded, displayed, and put up on "top user" charts.
Is this effect an issue that may affect the quality of the questions and answers? If so, is there any particular thing we should do, or at least be cognizant of?