Privacy in Halo 2

Here’s a question and answer from Bungie’s latest weekly update:

I see that my stats are available on the Bungie web site. Is there a way to hide the information so that others can’t see it? I can look up games played for everyone in the system. – That doesn’t appear to maintain any privacy.
Fraid not. It’s in the terms of service agreement. If you link your Gamertag, your stats are public. We have had complaints (seriously) from folks playing hooky from school or work that they can be busted by the system. At this time you link your Gamertag, your stuff is public. That may or may not change in the future.

One of the cool things about Halo 2 is that there are a lot of stats publicly available on Bungie’s website. For instance, I have an RSS feed of the games I play online. That makes it possible to analyze gameplay in Flash or even Excel. It also makes it really easy to find out that I was playing Halo 2 when I should have been, say, cleaning my apartment.
Social software developers have been wrestling with these issues for as long as there has been social software. ICQ made you confirm that you wanted to be on someone’s buddy list, AOL lets you block someone so that they can’t see you online, email clients generally ask permission before sending a read reciept. Even XBox Live lets you appear offline in your friends’ friendlists.
Bungie needs to make the public stats opt-in, or at least exclude games where the person is pretending to be offline from the public stats. That works from a UI perspective: someone who didn’t show up as online on Live also wouldn’t show up as online on Bungie.net. Am I missing something? Is there an advantage to forcing stats to be public instead of allowing people to opt-in? (Thanks Stephen for the tip)