It has. There are a number of "reputable dealers" I will not buy Golden Age or even early Silver Age from raw due to undisclosed resto, undisclosed tanning, brittle pages, adjusted scans, overgrading, etc. We have discussed some of them here ad nauseum in the past, and many have continued to loosen their grading over time to try to squeeze out as much as possible that is not worth looking at their tables/websites at shows.
As far as part time collectors/sellers, go to a show and look at the grades and prices that most of them have on their books. They tend to be one to two grades too high (some way worse), priced above GPA, and most do not know how to detect resto or are trying to pass restored books off as unrestored (e.g. the scumbag seller from Vancouver selling undisclosed restored GA and early SA books at the Calgary Expo a couple of years ago). I am fine with that since it drives buyers to our tables first to spend/put purchases on hold, and then they come back shortly after to add more to their piles. However, I do know collectors my age (mid 40s) that used to spend several $10Ks/yr who have stopped buying altogether due to getting burned by said sellers, which is not a good thing for the hobby.