That graph is nice but this is the real graph you want to see:
https://img.skitch.com/20120331-ft3faju2jpqseq3ucff1fgi31h.p...
That's the "estimated" (all open trials) revenue growth for Freckle over its whole life time. Look how stagnant it was, then slow, and for how long. And compare that to now :)
NB: real billing, trailing a month behind any given date, is 5-15% less than the estimate (due to trials not continuing etc).