beware blog spam!

The other night I was (foolishly?) inspired to post some messages on two Dean blogs (Dean Nation; Change for America) about Kerry's vice-presidential choice (as if my last minute personal opinion might actually sway anything!) I included a link to my webblog (which I haven't really tried to publicize very much) and within six hours I'd gotten nine porn comments inserted in various places. Just deleted them all, but wondering, if I did decide to enter more public cyber-conversations....I could spend hours/day just getting rid of the crap! How do other bloggers prevent this?