I'd say that being around people fuels my creativity. I don't need to be around people while I am in the process of completing a task, but when it comes to generating ideas, people in my vicinity can be quite helpful. Other people offer a stimulus with which I can work. Somebody says X, I hear it, and it causes a cascade of ideas to go off in my mind, leading to Y to Z to AJK!#AJ%$GD&RI. Then I can talk about my ideas and have them critiqued/enhanced by an outsider's perspective.
It's definitely more helpful when I know the people too; with new groups and acquaintances, I'm more focused on analyzing and understanding than I am on generating my own novel thoughts.
However, people are usually a distraction once I am actually working through the nitty-gritty process of realizing an idea (ie writing papers, researching, carrying out a project). I'm pretty easily sidetracked, and if somebody says or does something that sets off a creative cascade, I'll subconsciously convince myself that the time spent focusing on my explosion of new ideas is worth the time not spent on the original task. It kind of sucks when I actually have a deadline, but it's ultimately more fun that way.
When I'm alone, I often find myself desperately seeking for something or someone to fuel my mind and set me off on some nonsensical tangent. I'm more content when my mind has some kind of buddy around.