No reason why BDSM dating shouldn't be going on, I guess sometimes an internet ad or even a paper personal ad might lead to a play date, but the difference to vanilla dates is here you have to keep at least some guard against winding up with a psycho or someone who is definitely not whom he/she appeared to be online. I mean, what happens if you are carried away and let yourself be tied up and then this nice guy turns 90 degress and proceeds to threaten you and rob you of your handbag?
I once read a feature about online dating in a daily, which also took into account more kinky sex contacts, and it put these points among others "if you are into getting restricted during sex":

*Don't leave out your phone number, your full name or your home address until you feel sure of your ground and have met the contact at least a few times.
*Always place the first date in a public place where you can easily leave if it turns out bad (a restaurant, a museum, a park etc). And make sure you can get home without relying on your date driving you.

This doesn't sound very romantic, and in practice I guess most of the time if you start dating somebody in the same town on a BDSM basis, either it's started as a vanilla date, you talk and you find you're both into the kink, or you've met in a fetish club or something and know each other a bit beforehand.