I would suggest adding a setting in the Forums control panel which would allow me to set the default selection of notifications by a poster.  I would like the site to default to subscribe to a thread if they post into it.  Then they could opt out before posting if they want. Even better would let me defaut the whole site one way and then allow users to over ride that in their user settings.

I did it myself by adding adding a checked property to the editpost.ascx page, but it would be nice to have this as an administrative option in the forum and would be easy to add.