There are instances in which this can be perfectly OK. A lot of the OK versus not OK decision will come down to what you as a user expect to give or get.
( Source: The Uptake | Quora Blogs, Branch and Other Things I Won't be Using )
I'm fully behind Brad's take here, and his challenges.
It's important to own your identity on the web, as much as possible. And there are places, mainly built around social networking and communications where it's difficult to adhere to owning your identity.
Still, I think it's always good to have a central point where everyone can read about you - whatever it is you post or say.