After a famously disastrous start, Facebook (FB) finally looks like a money-maker for true believers. The stock is 10% higher already in 2013 and over 50% in the last three months. While impressive, those gains were really the easy part for the battleground stock. The company is generating buzz this week after announcing a mystery press conference scheduled for next Tuesday. But the bulls will need to hear something exciting enough to keep the stock from giving back those gains.

According to Kyle Harrington, managing partner of Harrington Capital Management, it better not be just another minor development in its advertising platform. "I look very closely at revenue and diversification within the revenue base," he says. Right now Facebook has a billion users and only one meaningful source of cash. It's enough to justify FB's existence, but it's not a growth thesis.

Whatever is revealed next week, it better have legs because the stock isn't cheap based on what we know now. Harrington tosses out the idea of a subscription model. Others have suggested retail. They could also do games, streaming or just about anything.

"I'm looking for some innovation and some new ideas coming out of Facebook," says Harrington. Until then he's inclined to play the stock from the long side but on pullbacks, not after the kind of rally FB has posted over the last 90 days.