maybe not a good idea. the career paths after mba and phd are dramatically different, i image it will be very difficult to explain to the school why you want two totally "opposite" things at the same time.
really don't think so. The ad.com. will think that you are not clear of what you want to do after school and neither do you really know why MBA/PhD now. As my suggestion, think thoroughly and try to make the painstaking choice between mba and phd.