I don't disagree, but at the same time, it does take an eye to be able to spot a good idea. If you look at Karim's LinkedIn profile (http://www.linkedin.com/in/jawedkarim), he worked at IPO and then helped to found YouTube--two not so bad bets (though I don't know if he got anything above his salary at PayPal). That said, if you assume that he's worked at only these two companies, he's already batting .1000.
A typical VC will make 10 investments for his portfolio of which 7 or 8 will go under, two may return 3-5x ROI, and one _may_ be big (but very unlikely it'll be the next Google). Since Karim is starting a VC firm, you could argue he's going into it with a better track record than most VC's, and the fact that he's played an active operational role in two companies matters quite a bit when it comes to evaluating deals. I'm not saying he's going to kill all the other VC's out there, but if he's got the dosh ($), why /not/ start a VC firm--espescially if that's his passion?!