Let’s just say, I’ve been a victim for an unnoticed, checked-by-default, Subscribe to Comments option. Oh, the endless deluge of new emails! It wasn’t pretty. So I applaud Mark Jaquith for no longer allowing such behavior:
In short, having the box checked by default was causing people to subscribe unwittingly, as it was an opt-out thing. […] A lot of users see if as being sneaky. Obviously if you want to edit the plugin to re-enable this option, I can’t stop you — but I no longer wanted to be encouraging use of this option.