Not a bad idea. It was something I had given some thought to when we just started on Perl Monks. I can see its usefulness the question is where do you draw the line? Obviously it would have to be
something configurable in user settings so you could turn it on and off. Do you want an alert for just the first response or every response... and for what nodetypes? That
problem tends to get more complex. It's something I'd consider doing and I'd be really interested to hear what types
of schemes for doing this people would find most helpful.
Perhaps have a user settings option to have
all postings in a marked thread (except your own) to be sent
to you by email.
For extra bonus points, stick a header, body or subject
cookie in there so a straight email reply is possible, with
the reply splicing nicely into the thread. (Time out cookies
Sort of a reverse mail archive...;-)