Thanks to online pinboard Pinterest’s fast growth, many retail sites are placing “Pin It” buttons next to items for sale as a sharing mechanism. Flash sales giant Gilt is taking the whole Pinning trend to another level by allow users to access special deals on pinned items.
This is an interesting approach to advertising. They're basically giving their customers and fans an incentive, in potential savings, to advertise for them. Done well and in a large scale, these types of activities could bypass publishers and media agencies, which advertisers tend to spend the most with.