They need a 64-bit binary one for the added register support and two for the extended memory address support. It can try to use more than 2GB of RAM if you play a game that is selectable using in-game options. The point, Inkedsphynx, is that the application can run itself into a 32-bit memory wall.
I think if a few killer games came out as 64-bit only, it'd force moronic gamers that strap hugely fantastic systems to 2001-era 32-bit OS's (yes, I'm taking a shot at XP) to finally wake up and smell the 64-bit coffee. In the Windows world, they write apps that could possibly do more than the old OS can handle because everyone demands it. It's weird in the Mac world, they upgrade the OS every 1.5 to 2.5 years, write apps that only work on the new OS, and everyone's (more or less) happy.
