Jim Goldman, a CNBC reporter, talked with WildTangent, a large publisher of online games and found Vista may prevent roughly 70 million gamers from playing web games on the Internet.
Companies like, RealNetworks, Time Warner, Yahoo and even Microsoft's Zone.com are incompatible with Vista. Alex St. John, CEO of WildTangent, says he thinks Microsoft “went extreme on the security issue with Vista”
Microsoft continues to say that Vista is the gamers operating system because one great bullet feature is the ability to play "Games for Windows" utilize the power of DirectX 10 and make game developers lives a bit easier. This may be true, for local games, but apparently not for the few million that play online via the web.
As with many things, additional security brings additional limitations and freedoms you once treasured. Oddly enough, Vista released without any "Games for Windows" launch titles. Maybe we'll see some games (web or local installs) soon?
source: cnbc.com
Thanks to CofC for the news tidbit