Why didn't you think of this?

John Goscha, at the ripe old age of 25 ditched a job offer at Goldman Sachs, and instead began marketing IdeaPaint, which is simply a paint that turns any paintable surface into a dry-erase board.

The benefit--besides being able to brainstorm on almost every inch of your office--is that the paint is half the cost of whiteboard and better-performing--you can leave marks up indefinitely, and they won't stain the wall. Of course, it takes a bit of time--you may have to sand the wall and prime it--but one other benefit is that you're not incurring all the carbon involved in manufacturing and shipping a whiteboard.

[Inc. via Dieline]