Cegstar. Was on Totse, then Zoklet. Life then got very busy, but I'm back again. I was all over in the forums, however I liked to frequent the technology section, and money money money.
It depends on what you're storing. If I'm storing a bunch of pictures (I do a lot of landscape photography), I wouldn't care. I wouldn't put my private info like my resume or bank statements on the cloud.
It's hard to say how many of them are real, I'm sure some are. I know if I were to go on a site like that, I'd be using a fake/new e-mail address without my name in it, and a pre-paid Visa.
Those might not be real accounts. You can sign up using an e-mail address and start using it before validating it. So I could use literally any e-mail I want to sign up if I'm not being serious about finding anyone on it.