The problem with a comunity deciding on this is bias. Everyone wants their own clan at the top. The only way to remove bias is to have a robot judge all clans, but there is no objective way to do this. So ranking clans in any way is flawed.
But it is obvious that some clans are better than others. An established clan with good players is obviously better than a nub clan with all whitebelts that can't control their toris. The only real separation between these two clans seems to be experience. But experince doesn't necessarily mean anything. There are people that have played since early 2007 and still suck and there are people that joined a few months ago, yet have major skills.
The only way to get true clan rankings would be to have a council of people who are completely new to the community go through and judge the entire history of every clan. This is both impractical and impossible, since most clan discussion happens in irc, and it would be a huge waste of time.