That's quite possible. But if you're not the kind of user who checks Twitter on a fairly regular basis--not necessarily more than once a day, but at least sever

That's quite possible. But if you're not the kind of user who checks Twitter on a fairly regular basis--not necessarily more than once a day, but at least several times a week--you're probably not the kind of user who's bringing in much advertising revenue, either. Maybe making signing up free but requiring the $1/yr to be able to post, or to follow more than 50 people. It's possible none of that would work, either, but I'm confident in saying there are at least tens of millions of people who do get value from Twitter. They've chosen a business model where having "merely" tens of millions of users may not be enough to support them, but I don't think that points to an intrinsic flaw in Twitter's concept--just an intrinsic flaw in their particular monetization strategy.