YehudaYona, thanks for finally answering the question. However, I thought they filter out shmutz, at least the pictures. I suppose you mean they are texting each other (and opposite genders) and the parent doesn’t know who or what. For this reason, I do not allow my kids to have cell phones until they graduate HS and go to Israel where they are required by the sems for safety reasons.
However, the comments here make it seem like there is some inherent issur in the site itself. That is what I cannot figure out, as most people here are adults, and if they have cell phones, how could Facebook be any worse? A far as sites go, there are probably tons of sites which are hundreds of times worse.