One of the interesting aspects of yesterday's announcement by Microsoft that it will be taking over Skype, is that both of them were effectively competitors until now.
Microsoft has already offered a similar service to Skype's voice and video calling service, within Windows Live Messenger, but it looks like it has never really taken off (or else the Skype deal would not have happened in the first place).
Put together, Microsoft WLM and Skype have more than one billion registered users (more than 330 million from WLM and around 700 million from Skype) and it would be tempting for Microsoft to merge both Skype and WLM into one single application and rule the desktop.
Doing so may decrease the total number of accounts, since there are many duplicates, and may introduce some significant technological obstacles in what would be the biggest user migration in the history of mankind. Should Microsoft opt for that path though, it would have a much tighter and coherent platform which will be vital to maximise advertising opportunities and provide it with a compelling selling point, an unbeatable voice reach.
On the other hand, keeping Skype and Messenger separate (at least in the short term) would mean that both entities could compete amicably within the company to foster competition. Doing so would also reduce the propensity of users to opt for other competing VoIP services such as Google Voice.
Either way, Microsoft is unlikely to kill a powerful brand such as Skype; the fact that it will live within the company as a separate division, Microsoft Skype, underlines this point.