Or you can just manually manage both instead of having iTunes automatically do all your sycning for you. This is what I do even with just the one iPod touch associated with my MBP.
No, you can specify what content from your iTunes you want to sync over to your iPod, it doesn't have to be on a different account. For example you can choose to manually manage content and do a drag-n-drop kind of thing. Or you can choose to sync certain playlists. It is all easily set up in iTunes.