Here in Australia many WS shops sell on line as do some producers of WS gear (eg Sails, Helmets) direct to the sailor. Generally I would go to my local WS shop first as they have a good sourcing network, but if their best offering is not quite what is wanted or too expensive an option then I will purchase online. So we actually have a good mix with which to work.
Established suppliers are reputable and buddies who have bought boards and sails online have found the process quite good with turnabouts and packaging pretty well streamlined even with trade-ins. However it seems to depend on a viable retailers to sustain the network as there is a lot of swings and roundabouts with hands-on v. virtual shopping.