Here's my use case scenario...

I create a new thread in the forum and want to be notified via my personal email when someone responds to it.

Allow the forum user to turn this feature on/off in their settings.

Then, when someone responds to my thread I get a notification message sent to my personal email.

This is really useful because I might not be checking the forum every day but do want to know if I got a response.

Also, have this same functionality when another forum user sends me a PM.  I often want to sent people a PM asking them for information but if they're not checking the forum on a regular basis they'll never see the PM.

* Note that eBay has this same functionality.

** I think email notifications will definitely help get more people involved in using the forum.

request sent