I've found that Stack Overflow likes to dominate the "My Sites" feed on "Filtered Questions". I've created a filter for all of the sites, without Stack Overflow. I just know that it would be nice to be able to use all sites except for ones that you don't want. I'm sure not everyone wants to take the time to click 80+ checkboxes. Even a "Select/Deselect All" in the site list would help.