"[Facebook and Twitter] are both verbs now, and that is a very strong indicator of how deeply they have penetrated consumer behavior," Liew said via email. "If their current capital is not sufficient to last them, they will be able to raise money (at some valuation -- perhaps not an 'up' round) because they are clearly generating value."
Facebook is generating revenues so I can agree the value statement, but not so much for Twitter. It has 6 million prospects and hasn’t monetized one of them yet. If it can, well then it has value, until it is just another free utility and represents the potential for value. That would be the difference between a prospect (someone who hasn’t paid you a thing yet) vs. a customer who has paid you something.
The next metric to figure out is “sustainable, measureable, profitable revenue from volume”… that neither Facebook or Twitter has (yet).