Is that really so bad? The worst I've seen is "this is a picture of John" which is not an abuse that's limited to social networks. And if this happens really often, you can complain to your friend about it. And if you can't complain to your friend, you can complain to abuse. And if abuse doesn't do anything (not likely) you can send a legal notice.
To jump from "a friend can mention me, talk about me, etc." to "there is no privacy anymore" is...well, I just can't get there, sorry.
Do we have privacy problems? Yes. Are these examples really selling that? No. I can't remember any case in which a friend sold me out for a trinket; if you do have a common example, cite it. That would really help us all here.