I guess I was assuming that these weren't serious web sites. Like, the OP said that they worked on a plethora of projects which sounded, to me, like lots of little side projects. I think it's ideal to work with artsy friends on those just like you'd work with techie friends. If you're doing something serious, clearly it's an employment thing not a buddy thing. However, sometimes you're doing a nice little project in your spare time and it's nice to build it with a friend who has a good visual sensibility and if it doesn't take off you've both spent some hours working on something cool and if it does take off you can continue working together.