Well I'm going to head off the predictable and boring "bubble" comments and say this: Pinterest has real value and a clear path to monetization through affiliate and/or advertising revenue. It's really a stupidly simple idea (essentially scrapbooking on the Web) executed incredibly well. Is it worth $1.5B? I don't know. I would say it's definitely worth more than Instagram for whatever that's worth (not a lot). I gue…
If you are left holding the bag, and they have to generate 1.5B in sales over their lifetime from this money to make it a worthwhile investment, then no: pinterest will never accrue 1.5B in revenue over its lifetime.
If you are not left holding the bag and this bubble keeps inflating, yes. It's easy to see how Pinterest can raise money at an even higher valuation with just a little more "spectacular" growth. (It's not really spectacular. More like a fad.)