With so many on-line stores now offering products, the question of customer service becomes as important as price-point. Someone posted about a company (auto anything)having the product, just to find out it was a month out from delivery. Usually the employee on the phone can only go by what they show. If the shipping department does not update stock quantities, then this is where the disconnect happens.
Some companies keep a tight reign on their inventory stock, and their on-line sales departments, with a IT interface, so as to avoid the above scenario. This keeps real time inventory currant. One company, Rocky Mountain ATV*MC (rm c) seems to be one of these. They list how many are available in what size or quantity. This is how it should be done. If your dealing with mom and pop stores, they either know their inventory quantities, or do the 'we can get it soon', without knowing the actual supply chain reality(delays).