Dear friend,
What you describe isn't exactly true. First of all, you can always disable forum auto-subscription from your user profile, and you can manually unsubscribe from any forum at any time.
Also, the 1.4 development version has a "mail digest" feature that lets you receive just ONE email per day, which contains all the recent forum activity. The digest has two modes, one of which just displays post titles and links to the actual posts.
So you probably just need the latest version...
Cheers, Jon