I think the bishop has a point, to some extent. The problem is not with social networking per se, but with the way how some people use it.
I don't think there is anything wrong with social networking, provided it's not a substitute for real relationships (which is what the bishop seems to imply). For instance, I use FB to keep in touch with my old friends whom I probably wouldn't contact as regularly (using the term loosely) otherwise.
The problem with FB is with flattening of social relationships/connections: everyone's a "friend", even though in real world, you have close friends, not-so-close friends, acquaintances and so forth. I suppose one could set up FB groups for them, but I never bothered. I share very little info on FB, just because I wouldn't necessarily be comfortable sharing pictures and comments (!) with just everyone on my FB friendlist.
And then, some people just add "friends" for... I don't know... numbers?
If someone starts treating these "friends" as proper friends, I can see a problem here. And hence the time bomb, or a grenade, I suppose.