Long long term is anyone's guess, but I think if the team stays mission driven and doesn't get distracted they won't have any problems with money. The company is still owned by employees, and the entire team is just 20 people. They don't seem to have a bloated stack or unnecessary features. They got a sizable initial war chest of $14 million from Twitter. When that runs out I bet adding just a "donate" button somewhere on the site will be enough to cover expenses.