These corporate friends are Etsy, a well-known online craft bazaar, Kickstarter, a funding platform that's probably just a publicity-hog anyway, and SoundCloud, a music-sharing website that allows a pinner to "pin" actual songs to their pinboard, with copyright-infringement issues of its own (see this article, although they are reputed to be meticulously pro-active in their infringement detection, quite unlike Pinterest).
Attribution doesn't absolve copyright infringement.
Halting copyright infringement may not even be on Pinterest's agenda. This may be due to Pinterest's very existence and popularity appearing to be entirely derived out of the feverish infringement binge of its users, enabled by the convenient pinmarklet.
One cannot be surprised that when Pinterest makes headlines about copyright, it's not even about copyright. It's just more smoke and mirrors to coddle its users into thinking they're working really hard for us creators, and to seat copyright infringement on the thrones of angels.
Attribution is necessary, but over-rated.
The "money" rests in distribution, not fame.