[xmasons]

This is a plugin request and I wouldn’t assume that it be rolled into bbPress proper.

A highly prized feature of allowing users to subscribe to sub-forums (via their account page) and be sent notifications (excerpts or full) of a new topic or reply. There are several plugins that capture parts of this, some quite close, but none that have the full functionality.

bbPress Notify
http://wordpress.org/extend/plugins/bbpress-notify/
Works great at sending out customized emails at a user role level. But it’s an all or nothing solution and does not let the user pick the subforums they’re interested in.

bbPress Digest
http://wordpress.org/extend/plugins/bbpress-digest/
Does a great job on letting the user select the sub-forums (from the user’s account) that they’d like to receive notifications from. Sadly, it’s only a weekly or daily digest.

Marrying those two plugins would produce a wonderful hybrid and would take some doing. I’m a little surprised that this feature has not been created yet, as it is used in several other forum software ecosystems.