As Peckesh said this has become a big problem for brick and mortar shops. I have even heard (though not witnessed it myself) of quilt shops blocking out all the bolt information to make it more difficult.
Quite honestly, if I see a fabric I love I buy several yards right then and there (usually 3 or 4). If I love it, I will surely find a project for it. Too often I have seen fabric I loved, did not buy it then and there, went back to get it and it was all gone.