While I don't have an account, Facebook has a ton of media-rich content available now. It's not simply a text repository outlining a casual acquaintance's boring and embarrassing moments. Those addictive visits to Facebook might include several videos, some casual gaming, or even catching a UFC mixed-martial arts fight or similar special event.
In fact, Facebook is one of the few things that might have the power to eventually force the ISPs to rethink their cap and overcharge strategy, as it might be big enough to move forward with technology despite the providers' efforts to crush it with unwarranted restrictions.
Although, we may have a bigger issue on our hands if Facebook continues along as it has been; a bit like releasing the lions to take care of the hyena problem.