I've been lucky enough to work with some amazing artists. I've also worked with people who have a hard time drawing a stick figure. But when you're brainstorming and problem solving with a team (which is what Limnu is designed for), it turns out that you don't have to be an accomplished sketch artist. You just have to be willing to pick up a marker and draw in front of someone else.
One of the very talented artists I worked with is a guy named James Buckhouse. He recently wrote an article called "If you can draw these three shapes, you can draw the Internet", where he demonstrates that with a circle, a triangle, and a rectangle you've got the building blocks to communicate almost any idea in your head... three shapes is, more or less, all you ever need.