Password Protected User Documents Not Blocked In Explorer

I created a second user last night and found a few folders in My Documents for the 2nd user had come from a Users/Public folder, when they were made in My Documents of the first user. So I went into the Users folder and looked into my first user and was able to access any folder despite being in the 2nd user. In Win XP I'd be blocked from accessing that folder because the user is password protected; in Win 7 that seems to be a security flaw since I'm not blocked.