I like your points but I'm not sure FB is just a "social movement". We are on the 2nd generation of mobile phone users. My 15 yo daughter didn't forsake a cell phone because I have one.
In my mind it's an issue of "Enabling Device" vs "Venue". Put it this way. Say your hang out as a kid was a bowling alley you used to drive to every weekend. As you grew up and had kids you took them to that same bowling alley for Family Night. When your kids become old enough to drive they'll probably still use a car but they probably won't choose their parents' bowling alley as their hangout.
Same here. Kids will still use Laptops, PCs and Cell. Phones but probably won't use the same sites as their parents when going on the web. Because the PCs are enabling devices that get you some place while the sites themselves are venues that you go to.
Mobile phones/contracts aren't social graphs in a similar sense that Facebook or IM networks are. If Facebook can become a utility in a similar sense that email and mobile phones are, then it can survive the generation problem.
