spankbri, had you been talking about BDSM in general, I would have said that the examples you give (clubs, internet porn, romance novels) have more to do with long standing gender roles than who likes to dominate (and, of course, the fact the men love porn!). Also, I'd point out that control freaks are likely to go either way, sometimes both ways. Paraphrasing Marilyn Chambers, show me an S and I'll show you an M. I think things are fluid and becoming more so, as gender roles continue to loosen.
as to spanking in particular, any bias is probably due to the almost infinite capacity of men to fetishize, especially on God's greatest gift, the female bottom. Yes, women claim to like male buttocks, but I don't believe they can muster the obsessive, singleminded devotion that men effortlessly bring to their objects of desire. Women generally need more than a body part or article of clothing. Anyway, that's my theory.
childhood story: I was 8 or 9 and two girls in their early teens came towards me as I was playing on the side walk. They ordered me out of their way, saying they would teach me a lesson if I did not move. So, being a little bratty, I threw a rock more or less in their direction. In part, it was a macho defense of all things "boy" from the usurption of power by, as I thought then, mere girls. But even then I knew what I really wanted was for them to teach me a lesson, even though I had no idea what that might mean. Alas, they just yelled at me and passed by, leaving me unpunished and seemingly triumphant...and extremely disappointed. Someday, I will get over it.