When I was a kid, my report cards would often describe me as "an independent worker."
It's one step above "doesn't play well with others," I suppose, but I wasn't exactly a collaborator. As an adult, I get similar descriptions on my performance evaluations at jobs and grad school.
But see, you know that saying about how if you want something done right? How you do it yourself? That.
Teamwork seems to stymie productivity, and even more so, creativity. A truly creative product is not just several good ideas mashed together. Rather, it's a set of cohesive ideas driven by a focused vision. When several people get involved, with their own mashups of ideas and egos, that focus is often lost.
Look at movies. The best of them are helmed by a single creative force (an auteur, if you wanna get fancy) whose vision bleeds through the necessarily collaborative process of creating a film. Citizen Kane, directed, written and starring Orson Welles, is generally regarded as a better film than the latest summer blockbuster directed by...well, who even pays attention to the director of crappy movies?
Look at music. The best bands usually have an overwhelming personality at the forefront. And if creativity was increased by teamwork, you'd think a supergroup with the best of several bands would dominate. But have any supergroups been better than the bands they were cobbled from? Have you heard that new Mick Jagger / Joss Stone / guy from Eurythmics song on the radio? Exactly.
Look at literature. How many of the greatest novels of all time have more than one author?
Look at technology. Few would argue that Apple's recent success doesn't have something to do with Steve Jobs' consistent and obsessive vision. His insistence on creating products that work and look good together, sometimes going against what a committee conducting a focus group would recommend, has lead to great success despite technology that may not always be the best in its class. I don't think Apple will now fail horribly without Steve, but they will lose something without a single creative force refusing to play well with others.
Teamwork is necessary for all but the smallest projects, and I've grudgingly gotten myself involved with several promising groups of great people lately. However, I think it helps to keep in mind that working as a team is hindering, rather than helping, creativity. A team has to take advantage of the additional time and resources afforded by a group, while fighting against the potential blow to artistry.
The best work tends to pop out after ideas have been bouncing around a single brain.