Kynes on 19 May 2010
I think he's talking about the first-third party ecosystem. Apple doesn't make games, Sony is trying to have the best games of the platform as 1st party, a la Nintendo. If Sony competes fierly with their 3rd parties, it makes harder for those third parties to have profits in their platform.
Edit: There is a big niche in the Mac platform, and with more PC like Macs, it's easier to cross develop. Valve only wants to earn money, and I'm sure that the cost/benefit ratio is bigger in Mac than in PS3.
