Superb - thanks mate - thats what i thought should (logically) happen as any other method would allow the other person to see that you have been online, at least since the last time they were on.
Also - i wondered about tags as well, when im online and listening to my tunes it shows up in my tag and of course the tag changes every couple of minutes, therefore the blocked person could just log in and out a few times over the space of a few minutes and check if your tags changing.
Que mayhem and hissy fits.
Would be a great blocker then really would it.