I was one of the people who wanted to be able to take collections out the parallel resource list. But I'm not sure it's a good idea to default new collections to 'off'. Power users will no doubt have lots of collections they don't want showing, but newer users (who are more likely to not understand or miss the tickbox) probably will want most of their collections as parallel resources.
One solution might be to default to on, but add a right-click menu to the parallel resource set which says ('Never show this collection here').
