User acquisition will always peak at some stage for most companies (the universe being the total number of people with access to the internet), so the attempt drive more usage is not surprising.

I do believe, though, that Twitter has lost its way since end 2009 and are largely making stuff up as they go along. It is also fair to assume that they will have pressures to ramp up monetization as they run out of time to bridge the gap between potential and actual revenues. Such is the curse of an insanely high valuation.