Twitter just moved into a new office, has been acquiring companies (remember, they're what drove Instagram's price up), and you really think they're secretly cash-strapped or something?
No definitely not, but the problem is that the clock is ticking and I think the FB IPO showed them what can happen when the right pieces aren't in place at the time of IPO.
No one is going to argue that Twitter has a technological advantage - their service is incredibly simple and could probably be completely replicated by a small team in six months to a year. Moreso than Facebook, they are relying on the network effect but the also monetize less than Facebook, so who really knows if they're ever going to be profitable?
