Yes, it would stall development of a lot of business. Many of these businesses are not necessary. Humans would start a different path of looking for what's actually useful rather than falling for what's out there -- or at least that's the dream :)

[edit] Onto your second point, that you need ads to promote price competition, I don't think so. There's almost no advertisement in many kinds of services like e.g. hair salons, but they still very much compete (price included). Also, huge majority of professional trainers do not advertise anywhere in my area, and yet we all compete on price and our customers know the range of prices that are reasonable. So information about price etc. flows quite well regardless of ads.