Why does Microsoft feel the need to buy other companies? Why do they not just build their own Skype version if they like it so much? How many people are going to lose their jobs now? Why do they employ all the brilliant young programmers if they are just going to buy up companies and not create new products?
More importantly, this is a textbook network effect market. Skype users are what makes Skype work. If MS announced they building their own, what odds would you offer me to bet I use it to talk to my Mother on it within 2 years?
