I think most people are confused about this beta version of iTunes, so here's the deal.
StoreActivationMode is a special mode for AT&T and Apple stores which puts iTunes in a special "Activation only" mode. This means that once an iPhone has been activated, iTunes will ignore it. This is useful because in normal operating mode, iTunes would start setting up the iPhone to be personalized. Obviously you don't want the guy at AT&T putting in his name and syncing his music. Basically, this mode simply disables everything but the activation process in iTunes.
There is also another mode that I found while searching in the app. This is called StoreGeniusMode. This mode is similar to the activation mode in that it disables features of iTunes' ability to communicate with the iPhone. Instead of allowing activation, it only allows software updates and restores. Makes sense, right?
So is this version of iTunes special? Eh, not really. It just has the special modes for stores. Totally useless to most people. But this does confirm that activations will be done in store. However, the memo also mentions that public versions of iTunes will still have the ability to activate or "unbrick". This means that you shouldn't have to take your phone out of the box at AT&T or Apple. It would be optinoal because you can do that at home. They'll only need to set up your account at the store instead of having it done in iTunes.
Does it suck? Of course, but at least we should have the option of unboxing our iPhones at home in big ceremonies.