Its definitely for the exposure, third party vendors just tend to get way more traffic than a person can generate for a personal website,although there are a few personal websites I see around that probably do pretty good for theirselves, I think its 50% here and at daz and 70% at commune that the artist gets. There ALL good places. Magnet , if I were you I would just take it as a compliment , Im not a vendor but I dont see it as spam , they were asking you to share your work. I dont think anyone can argue that the more exposure you get the better off you will be if youre trying to profit from your work.