Anecdotally, it's happened to my father and brother. There are bot-made accounts on Facebook with their biographical information and pictures, taken from Wikipedia. Apparently it's standard practice for "notable" persons who don't create their own pages.
Not that I can quote but I have friends at LinkedIn, Facebook (and Yahoo who does it too) who specifically work on this feature. I would be shocked if Doubleclick (google) et al weren't doing the same thing.