This happens with the majority of acquisitions that, as soon as they are acquired they see an uptick in signups. The uptick would be more interesting if they announced it in a month’s time or in an even longer period of time. There are several reasons for this including, the perception of “X has acquired them and they’re a massive company which means that the service will be around for a while” (which is not necessarily true) and the fact that, the acquired company gets a lot of press from areas they may previously not have done so they get new users either as customers or simply joining to ‘look’ at the service – although they may not become actual valuable users – by those I mean ‘look’ at the service, I’m talking about other employees of the acquiring company, shareholders of the acquiring company etc.