With all the excitement, it's easy to forget that the video-sharing pioneer's business so far amounts to a whole lot of expenses, not much revenue, and no profits. (...) YouTube spends a tidy, and growing, sum to stream its short clips. Current estimates range from $900,000 to $1.5 million per month. Much of that goes for computer servers and transmission bandwidth. But because the company is charting a delicate course in how it handles pirated videos, its legal costs could balloon if lawsuits start piling up.

Even more important, though, is the tricky question of how YouTube can make money off its phenomenal growth while maintaining the promise behind that popularity. YouTube could easily alienate its users by overwhelming them with ads. And the startup has to figure out how to attract a broader group of marketers by filtering more for copyrighted or offensive videos and by creating more channels of similar content.