Their scheme might look like this:

Skype IPOs. Yay! Their on the stock market trading at $40/share!

Skype gets DDOS attacked and goes down (which has been happening… maybe not because of DDOS attacks)

Skype’s share price plummets.

Hackers proceed to buy up all the Skype shares at something south of $6/ share.

Skype’s services recover, and their stock price rises again.

Hackers sell and make a nice buck, proceeding then to wait for the next web start-up with a fresh CEO to IPO.