If you're talking about photo ads for products like CK underwear or a men's cologne, I imagine the companies involved might technically call it theft but wouldn't complain about it...they might even be quite happy about it. They would see it as advertising that they didn't have to pay for, sort of like viral marketing. Remember, the product they sell is NOT the photo ad, it's the underwear or bottle of cologne. If I were CEO of CK, I'd be delighted that bloggers were plastering my photo ads all over the internet.

Porn is very different. When a blogger shows complete photo sets and videos, that IS the product, not an ad for the product. The viewer is getting the entire product for free rather than seeing an ad which may persuade him to buy a physical product like underwear.

Kevin