It's a stealth brag that they have friends on a social networking site. This is insignificant to most of society but to nerds, having friends in general, even if they're online, is a pretty big deal. It's kind of like saying "My girlfriend keeps choking on my extremely huge cock!"
See also: Posts here on The Bore that say, "On Prole's Facebook, I saw this..." notice the exclusionary tone about a fucking Facebook account. Nerds will always have weird hangups about friends. It's unfortunate that the adverse effects of high school still impact grown adults 10-20 years after the fact