Sure it's going to be risky business but for example if they invest 100 million dollars for a stake in 5 new companies, it can only take one of them to come out with a break out hit
The breakout hit rate in the industry is far, far below 1:5.
The Xbox360 will have 1000 titles (including Arcade) at some point this summer. How many of them would you classify as "breakout hits"? How many are new IP from relatively small studios and classify as "breakout hits"?