I don’t think they’ve degraded our concept of relationships (past tense, unchangeable) as much as they are degrading the concept (present tense, changeable).
It’s easy to forget that the entire concept of an online social network did not exist ten years ago. I agree that it’s important to recognize both the good and the bad they’re doing and to use that awareness to help shape the future role they play in our lives.
They are tools for communication, much like the pen and paper have been for thousands of years. Of course these new tools are far more powerful than pen and paper and as such they deserve a lot more care in their usage.
We’re in the pre-birth stages of this communication revolution and it will take concentrated effort on our part to help guide this shift in the best direction.