[Mailman-Users] Massive Reduction in Subscribers?

[Jim Tittsler]

 > I guess it could also be something else... Do bounces ever cause
 > unsubscription, not just blocking? Would there be something else? It 
does
 > seem strange to lose that many members so quickly.

Do you run the "cron/disabled" script to send notifications to users
that have been disabled by bounces?  When all of those notifications
are used up, the user can be deleted.

 > Any pointers to figure out where these folks went would be great.

What does mailman's "subscribe" (and "bounce") log say?