Found a really great link via Creators Against Pinterest that went at the Pinterest issue from a different angle, Thomas Knauer talks about how reducing images to eye candy decontextualizes images and why Pinterest is a pernicious environment.
It's interesting because I was trying to figure a way of displaying my images that includes some context besides my url signature and meta tags (all that can just be ignored or removed). It's easy enough to give context on my blog, but when people grab images from google search none of that context goes with it.
This is an old pic from 2008 that I thought I would experiment with.
I particularly liked Thomas' quote "My concern .... is that this valorization of surface runs essentially counter to the fundamental connectedness of the tradition in which we all are working, the profound value of context".
On the other hand
as a marketing tool
But that marketing only works if pinned images link back to the source and often they don't. Spam sites scrape your images as a means to redirect image search traffic to their sites.
Which is why having your url somewhere on on the image might help, especially if you are trying to sell or licence a particular image.
Anyway just my humble thoughts. Like many I am on a never-ending learning curve.