Facebook ceased to be cool once enough of its original userbase started having babies, thus compelling their parents and other older relatives to join. :)
Indeed. The main idea behind Snapchat was the the parents cannot monitor what you send.
Not quite. It's more so just that Snapchat is new and is something that not everyone was already on. However, that's changing quickly...
I agree, but that newness had to have an appealing idea, not just be a clone of FB. These things are like TV shows, with a run of 5-7 years on average.