Is there a website that you can post info about the people you've met on dating site?

Post some here. Pretty please with sugar on top.

There was a website where people could warn others about exes and unsavory people they have gone on dates with, but it was shutdown because of the potential lawsuits people could get for defamation or something.

Slander.com ;)

That sounds like a great idea. But dangerous. You might find yourself on it someday.

Loose.com ;)

I’m not a lawyer, but if what you say about someone you met on a dating site is negative but factual, I don’t think it’s considered to be slander.