Step 1: the cool kids spot a new place and start hanging out there.
Step 2: the first signs of the popped collared masses show up, pushing the cool kids out as they realized the lame-streamers have spotted the new venue.
Step 3: the masses start reviewing the venue on Yelp and in local hipster papers claiming it is the hot new spot.
Step 4: the suburbanites located a 30 minute drive from the venue (without traffic) read these reviews and start frequenting the venue, causing long line-ups outside.
Step 5: the masses proclaim the venue to be uncool and/or played out and move on to the next best thing.
Step 6: the venue becomes filled with 30 and 40 something divorcées who are trying to be cool and crossing their fingers that they win the lottery so they can avoid having to do the whole Match.com and eHarmony thing.
Step 7: the neighbourhood that the venue is in becomes fully gentrified and the venue is sold to some entrepreneur who wants to make it into a Starbucks or fake Irish pub.
Facebook's history follows this same pattern:
Step 1 (2004-2005): The place for cool university kids.
Step 2 (2006-2007): The 20 somethings show up and proclaim how awesome this new phenomenon is. Not to be out-done, they claim ownership to the new network, and get their friends to start checking it out every so often instead of MySpace.
Step 3 (2007): The young professionals show up and start discovering that their old high school sweethearts grew fat, old, and unhappy. They revel in the spectacle. The cool university kids start complaining that the place was better when it was just Stanford, Harvard, et al.
Step 4 (2008-2009): Your mom, dad, uncles, and aunts show up to the show. With every Like from their mom, 20 and 30-somethings start cringing and trying to figure out how they can lock down their privacy settings. Word starts leaking out about how the cool kids are now using something called Twitter.
Step 5 (2010): The first murmurings about it being cool to not be on Facebook are actually taken seriously as every 50 year old and their day job at some boring Fortune 500 company setup shop with a Facebook Group and a QR code advertisement. "Quit Facebook Day" becomes a movement. The cool kids, having adopted Twitter en masse, now start being over-run by the 20 and 30 something professionals who are desperate to find their new fix.
Step 6 (2011): With most actual action happening on Twitter, Facebook is relegated to the social networking equivalent of having brunch with your friends. It's no longer the cool party spot. It's just a place you go to brag about that other cool thing you were up to the night before.
Step 7 (2012): Facebook announces its IPO and officially becomes the Hotmail of Web 2.0.