Your ID Is Showing
My Good Friend Kirk McElhearn points out that your iTunes Account ID is accessible to any smarty who can open your iTunes Plus files. Derek DeLong extrapolates this phenomenon to suggest that if you P2P your iTunes Plus files Apple may be able to track you. Seems to me another sort of smarty could wipe any account info from the file anyway (along with any other purchase info) if one really wanted to nefariously P2P.