The internet has increased the circulation of equipment to the point where you don't have to go on an adventure to find used gear. Once the domain of dealers who would mark up used gear, the market has turned into the individual seller and buyer and the internet has circulated the information on what's available, effectively elbowing aside the dealers in this market. In addition, and most important IMO, is that the exchange of first-hand information from us grunts in the trenches really has shed a light on audio products that you would never get from a dealer - instead you would have to rely mostly on audio publications, which themselves are problematic (another topic altogether).
Not only that, but new entrants into high end audio, such as Supratek and Teres, have taken advantage of the word-of-mouth power of the internet to suucessfully sell their products at a lower cost by bypassing the dealer network. So, yes, it may be hurting the High End dealerships - but how many of us are willing to forego information or pay more than we have to?