Dynamic distribution lists with opt-out capabilities?

After posing this question to several vendors in our IdM evaluation meetings, I actually think that there are no current solutions out there that will allow you to create dynamic distribution lists with opt-in/opt-out capabilities. I'm not entirely sure why one might want to do this, but being at a university, I can do things simply for academics' sake, right?

Here's the scenario:

• A school wants to offer a newsletter to all of its Geology majors. Maybe it will provide information about guest lecturers or other events. This DL could be pretty easily set up in Exchange 2003 (or 2007) using a query-based distribution group (ie: an AD attribute matching "studentMajor=Geology"). As new students join the program, they will automatically receive the newsletter because their 'studentMajor' attribute will match the filter criteria, without any manual intervention from list owners or AD administrators.
  
• However, maybe there are students with other majors who have an interest in geology, and would like to receive the weekly email newsletter. Or conversely, a Geology major who wants to reduce his inbox clutter and wishes to opt out.

I realize that you could construct a complex filter for the mailing list, which would take into account these other two situations (an opt-in, and an opt-out). So now your filter string for the DL would look something like this (in quasi-code...):
(((studentMajor=Geology)(|optInDL=Geology))(&!optOutDL=Geology))

(roughly translated: your major is Geology, or you've opted in to the DL, AND you have not opted out of the list)

However, I haven't really found anything out there to do something like this. There are some products from Imanami called SmartDL and WebDir, though I'm not sure they're a fit either. SmartDL allows for the creation of query-based distribution groups (just like in Exchange...), and WebDir offers end-users some control over their AD attributes. I guess a combination of these two products would (somewhat inelegantly) accomplish the above scenario.

Any other ideas out there?