I don't think the effects are that negative - there's plenty of violence, sex, drugs and swearing allowed in an M-Rated game or an R-Rated movie.
Sure, some developers shoot for a certain rating and change their design philosophy, and AO games and X rated movies aren't sold in large retailers, so developers have to go into an adult rated game trying to stay in the confines of the M/R rating, but like I said before - an ungodly amount of adult material can pass in the M/R Rating.. it basically comes down to Explicit Sex being the only thing that breaks the rating. and I've seen a graphic blowjob in an R movie
So no, I don't think it's negatively impacting the industry.. in fact, I feel that it's mainly a positive impact, as it puts the content control in the hands of parents, rather then in the game developers or individual stores.