Looking at their adjusted EBIDTA, it looks like they managed roughly the same amount in 2012 as in 1st half of 2013. That definitely shows that they are aggress

Looking at their adjusted EBIDTA, it looks like they managed roughly the same amount in 2012 as in 1st half of 2013. That definitely shows that they are aggressively driving to profitability. Top line revenue is not looking quite as impressive, but 2012 is shown at $317 million, where as H1 of 2013 is shown at $254 million. If you assume same revenue levels for H2 (no idea if that's a valid assumption), you are looking at $508 million for 2013 or a 60% growth in revenues. Add to this the sentiment comments made by others about how mainstream twitter is, and you definitely have decent justifications for high-ish stock price.