if you go to David's: they will make you fill out a profile, make sure you check the tiny box at the bottom (or have them do it if they insist on filling it out for you) that says NOT to sell/share your info.
They may try to argue with you, but be firm, "I do not want my information shared with anyone". There IS a way for them to indicate this and it will cut down on the spam fallout immensely.