It went unmentioned cause it wasn't really relevant in the article. The danger all of these type of applications face is that it's very very hard to tell if yo

It went unmentioned cause it wasn't really relevant in the article. The danger all of these type of applications face is that it's very very hard to tell if you're delivering anything of value, when you're not charging money. Some people just delete their account. Some people stop logging in. Some people log in but far less often. Some still log in as often, but are bored when doing so. Some do it, but are really just waiting for the next big thing. The risk of the high valuations is that all of these guys look like potential users, people who will click adverts. Bebo had a shit load of active users when AOL shelled out $850,000,000 for it. The danger is that no one ever checked if any of the users actually gave a shit about Bebo.