I'm currently working on a little project for the Mac App Store. The app does a bit of cross-scripting with iTunes, so to make sure that everything's kosher with Apple's Sandboxing rules, I enabled the com.apple.security.temporary-exception.apple-events entitlement with a value of com.apple.iTunes.
And… nothing worked.
After about half an hour of stressing out, Googling, and ultimately failing to find a solution, I tried entering com.apple.itunes (note the lowercase).
It worked.
So, entitlements values are case-sensitive, and apparently all lowercase! I didn't see this mentioned in any docs anywhere (that's not to say it isn't — UPDATE: Yep, it's mentioned in the docs *facepalm*), so hopefully if you stumble across this while Googling, it might save you some time and hair.