I guess I agree with SteveS. Some people would find it an annoyance. I wouldn't even use the board if it didn't notify me. I just couldn't see going in five times a day to see if one of my eight threads have had a post since I last looked.
There are times that there may be a user and I posting back and forth several times within ten minutes. I wouldn't want to keep checking.
I guess it's like email. Outlook tells me when I have an email otherwise I don't need to check it.
To each his own. A preference would be best.