In short, dont be so hasty to judge.
Twitter might still not have a viable business model, but they can experiment (now that they have a huge user base and data) and try to find one. While its not easy and obvious at times to find a viable business model, just reaching the sheer distribution scale as Twitter's is a huge hurdle in itself that very few incumbents will ever reach.
The infrastructure of Facebook and YouTube and Twitter could be replicated by a small team of smart developers in a matter of months, probably costing only a few million dollars. The only thing they have going for them is network effects, which are less powerful than we think when there is a viable competitor (e.g. MySpace being overtaken by Facebook).
Part of $41mm is because of the team, but I'm betting most of the money is because of the long term, ambitious vision they have for it. But to get there, they have to release a decidedly short term vision product and build from there. This is probably just the launching pad.
But still, $41mm before any sort of traction or any proof of a userbase is really crazy