There exists a fascinating little creature in nature called a lemming. What’s remarkable about this rodent isn’t its shape, nor its size, nor its long soft fur. Rather, what’s fascinating about this little creature is what happens when you put a bunch of them together, can you guess what it is? Yes, yes, they do have a lot of sex but something more remarkable than that happens. These seemingly disparate brains begin to stop working. Not just stop working, but stop working in a wonderfully fantastic and tragic way — they commit mass suicide. On occasion, this single unified herd of lemmings hurdles themselves off a cliff into the ocean jumping to their tragic demise in one of nature’s most twisted spectacles. 
Now’s what hard to imagine about this scenario is how the lemmings can possibly think to do this. Sure, the first lemming might justifiably have to run off the cliff because he’s got no place to go — either get trampled by the crowd, or take your chances going off the cliff. The next guy in line doesn’t fare any better because he’s got to follow the first one off the cliff, or else be trampled by the group. The ith rodent doesn’t know any better because he’s just sees everyone in front of him running and everyone behind him running, so what else is a rodent to do? Now here’s the interesting part: what’s the last rodent thinking? As he approaches the cliff he sees that everyone is jumping to their watery grave. So he has two choices: join the charge to his furry demise, or stop and think about what comes next. Guess what happens? 
That last rodent is infected with a particularly viral meme: the “they must know something that I don’t” meme. They must know something I don’t know. They can’t all be wrong. They can do all your thinking for you? There are countless papers, books and evidence of this social proof phenomenon happening not just in our furry little friends the lemmings, but in every imaginable human society that ever existed.
Looks like everybody on Facebook, Google+, Twitter, Tumblr and every other social networking site is getting ready to jump off a cliff. What are you waiting for?