Well I do use facebook to keep up with organisations and individuals working in the field of environment and conservation. There's no website out there that can collate information from dozens of organisations and hundreds of individuals (conservationists, researchers, photographers) all related by a single cause, and present it. I don't use facebook for games, nor stupidly post personal stuff like photos, addresses, phone numbers and the like. Until a large fraction of all these organisations and individuals set up multiple accounts on multiple sites (many of them aren't even on Twitter, let alone G+, tumblr and more obscure ones), I have to weigh the potential privacy benefits versus denying myself of information interesting to me. For the moment I stick with FB for this purpose, as I figure even if they were to data mine my profile and posts, all they'd get is a lot of ecology related stuff, and nothing really personal.