Thats twitters big issue right now. They just received another round of funding because they aren't making any cash. They changed their terms of service so they could start showing ads in the future.
The two posts above mine are dead on. It's the dot bust model lingering around in 2009.
It's not as bad as the 90's though. Back then site owners didn't care about their sites. They were in the business of securing investment money to pay their bloated salaries. It still goes on to an extent, but a total phony can't get away with it anymore.