I'd have agreed with you a year ago, but the WordPress debacle shows that the BDFL concept really hangs on the "benevolent" part of the job description. If your BDFL goes rancid your only option is to fork, and hostile forks are very difficult to pull off because it almost invariably forks the community.

The BDFL archetype is basically Plato's philosopher king. It's a nice and appealing idea in theory, and works well if you get a good one (Matz for Ruby, by all accounts). But it's risky, and it's hard to be sure yours is actually benevolent and will stay benevolent.