David H Wong
Banned
Ad revenue
It would have to be the POTENTIAL for ad revenue, ie Twitter and Reddit have both never made a profit, but they are worth a ton because everyone figures if the audience is large enough, in the future you can do SOMETHING to make it pay off.
But with Reddit that's even considering they both run ads AND charge for "Gold" accounts, AND don't have to pay for any of their content. Even then, they run in the red every month. Because banner ads don't pay jack shit.