This is really weird. I updated my iPhone to iOS 5 today, along with iTunes to version 10.5. According to Apple's own documentation, I should have an option to "sync with this iPhone over wifi" under the Summary tab when my iPhone is plugged in - but I don't!
Since I can't enable it, my iPhone doesn't "see" my computer when I go to Settings > General > iTunes Wi-Fi Sync on my iPhone, even though both are on the same network.
The only thing I can think of is that it's because I'm running OS X 10.5? But I still have iTunes 10.5 and iOS 5, which is all that Apple says is required (they don't list a minimum required version of OS X itself).
Anyone have any idea how I can enable this?