Twitter has been doing quite well on cell phones, business model or not. Yet the question remains: how exactly does the company plan on making money? (Especially if Facebook isn't buying it.)

"Potential investors and technology analysts are notoriously cynical of Web start-ups that haven't yet established a business model," a report in today's LA Times said. "YouTube and Facebook were pelted with those same criticisms in the past, and now, the skeptics are demanding the same from Twitter—shake your money maker."

One idea suggested by Twitter co-founder Biz Stone is to charge for corporate accounts. But he refuses to go the ad route, leading the LA Times to speculate that third-party developers may jump on that opportunity instead. Some already are, including Twittad, a service that sticks ads behind Twitter pages, and Magpie, a text and link ad insertion platform. The community is up in arms about this, though, as the report said.