From what I gather, this will be happening more often at Google. They build their products using small, independent teams, but as these products get bigger they need to be integrated with each other. For instance, there are separate applications for Google Chat, Messanger, and Voice (I think there's another one out there too) and they can all have seperate logins and contact lists. You can sync them fairly easily, but it makes more sense to combine these programs into one system, using the best features from each.