Imaro
Legend
Even when they don't (see my post above) it can at least give them a different perspective on process. And it works both ways; if you have someone who mostly GMs it can pay to have them play once in a while to help keep perspective.
I don't necessarily disagree but as stated before, if someone knows something is not their cup of tea or really isn't interested in something, then I'm not going to try and get them to do it because I think it's going to benefit them... i.e. I know better then they do.