Glenn (I assume),

Race tire sales is a very structured business. It involves contracts for evey deal and region (Both written and verbal) If all contracts are followed, then life is grand and everyone is happy. Online sales of race tires evolves this to a little grey and complex situation. This is the case for a couple of major reasons:

1. Online sales can easily cross the implied boundaries set by the contracts mentioned above. The dealer that hosts the online sale site might not intentionally cross that boundary but the buyer (racer) might. The e-commerce dealer should have the decency to not ship the tire outside his region but that is their discretion.

2. The local dealers, like myself, are in business only to serve you. Race tires are not (supposed) to be sold to the general public. So the online sales should only be to get tires to you, the racers. When a racer buys tires from anyone besides their local dealer it really does affect that business and consequently, the riders that the business supports. The race tire business has a very small profit margin. Very small. (Thus, why I keep my job as an engineer)

As a consequence, this puts the local dealer in jeopardy of not making a profit or even breaking even for the year! If that happens then continued support for your area will defintely be affected.
As an additional side effect (not to undermine the knowledge of riders) but I have been a part of several cases where a rider has ordered a tire from someone else rather than their dealer to save a couple of bucks. Only to order a softer or harder tire than they could use in any of the tracks in their area. The few bucks they saved turned out to cost them $300 in the long run.

So in the end, develop a great relationship and buy from your local dealer (including take offs). This is the best thing you can do for you As long as they care about you as a customer, they will do what they can to be at the track for service with no additional charge (something an online site can't do), give you a fair price and to give you the best advice to save you the most money in the long run with great race results.

To finally answer your question, online sales has put a hinder on the overall business. I have had it affect my business personally.