In my opinion, I think you should go for it. The way I'd look at it is like this: you will most likely always have a chance to work for some reputable valley company. However, you may never have the chance at your own start up again. This goes along the same lines as what davidw posted, but if I were in your boat and did not take the job, then I know later on down the road, I would be wondering "what if?" I wouldn't want to have to live with that.