to suck money from people, shamelessly, in return for a thought that you have a minute possibility that you might get laid?
eh, sometimes I met my last bf on one, we dated for a few months. I wasn't too impressed with him but that wasn't the dating site's fault. He paid to msg me though, it was with lavalife... I liked it cuz you could peruse other peoples profiles for free, it only cost money to message them.
I've looked around on a few sites (friendfinder, adultfriendfinder). For me the biggest issue is that there are way more men then women, and so all the women on the site get flooded with messages. If you're a woman, that's all fine and dandy, but if you're a guy, the chances of getting a message in return are slim to none.