Take the TLD away from the .tel system, put it on tel.com and give users tel.com/user instead of user.tel and what are you left with? The same exact system, just a slightly different way of getting there.
So does a social site having it's own TLD make it any more professional than other social sites like MySpace or LinkedIn? I personally don't think so. What it actually boils down to is features.
If I was in a position where I needed to tell someone how to find me, but I couldn't tell them the actual contact method or give them my full .com site, would I be better off telling them about me.tel or
www.myspace.com/me?
For business purposes, I'm taking the MySpace method 99 times out of 100 simply because everything on the .tel can easily go on the MySpace. Plus I could put all sorts of promo materials on the MySpace.
I'd like to see where people are getting their .tel's to rank among premium keywords where there is a lot of completion and real money to be made.