Here's the thing: While users may not be paying with their dollars just yet, almost all of them are paying with their time. So, it's not completely absurd that certain companies are able to attract such capital if investors continue to recognize huge potential in the long run.
Pintrest has about a gazillion ways it can monetize. I'm really anxious to see how they do it.
Just today while driving in the car my wife said "Cool, I just got a [push] notification from Pintrest that a fabric I pinned at JoAnne Fabrics is on sale".
Pintrest is a gold mine and my guess is that they've got a rosey future that doesn't end in acquisition.
Snapchat has an engaged audience. I can't imagine how they'll really monetize their user base in a meaningful way. But they're a really attractive acquisition opportunity for a bunch of companies.
Obviously investors might be more bullish on Snapchat's revenue generating opportunities...