A Bitcoin rich list would be great PR (perhaps we could get The Times to sponsor it).  However, are people really going to want to associate themselves publicly with BTC given the dubious nature of laws/regulation surrounding BTC at the moment?

Perhaps, with an anonymous way of associating yourself with wallets via a pseudonym of sorts (certainly possible) this idea could be fun, but again, nothing to stop me saying "I'm Bill Gates and I own this wallet"

Ergo, no way of proving claims one way or another.