When I collect and process, I find that I tend to want to "collect personal stuff" while I'm sitting at home on my computer, and "collect work stuff" when I'm at work. It might be because I can think of open loops more easily when I'm in the relevant context, but it might also be because I know I'll find the sheer number of open loops in EITHER dimension overwhelming.
Does anyone else do this? Is this "acceptable" or does it indicate that I'm trying to sneak around the principles that make GTD work? For some reason, a mixed list of personal and work ideas (especially the someday list) actually makes me want to physically cringe.