Originally Posted by Jaywalk3r

I ride aggressive and fast compared to most commuters I see; I use BMX pedals. (They could be more accurately described as nubbed than spiked!)

I would hypothesize that riders who get into urban riding from a road racing (whether or not they actually raced) or mountain biking background tend to use clipless, while those who started out as urban riders tend to use some sort of flat pedals.