http://en.wikipedia.org/wiki/PageRank
The most successful search engine (and possibly most successful company period) agrees - rank importance by the importance of those who give it importance.
The logic behind this is the same logic that gives reputation in the first place - the community trusts your opinion. So you are granting trusted users the ability to leverage the trust they have been granted.
In general, much of "Jewish learning" is related - someone with experience in how to learn will generally have a better idea of what fits into the system and what doesn't. Someone who has earned 50000 reputation is probably not a bumbling fool who happened to answer a few questions about how to translate words on a medallion. But someone who has 500 reputation might be.
Someone who has earned a high reputation gives some indication of their experience and exposure to Jewish knowledge, and one does get a sense of the methodology of Jewish thought, and what just seems questionable. It isn't a hard science, but you do get a feel for Torah Judaism's thought patterns. Granted, this wouldn't make sense to differentiate between the guy with 250 reputation and the guy with 500, but demarcations could be drawn - say, less than 5k, 5k - 30k, and 30k+? I'm sure the SO brainiacs could run some kind of diagnostics to figure out what numbers would make sense, per site.