Pinterest has noticed that many people are using the site as a social bookmarking site so they are making improvements to the process. I don't know about the follow-nofollow status of these links but this looks like a good link building opportunity.
They made this announcement in an email to users today so those with accounts may have seen this:
Hi there!
Lots of people use Pinterest to find and save things they want to read. In fact, more than five million articles are pinned every day.
We're starting to roll out article pins, which gives pins a new look. Now, pins from media sites will have the headline, author and story description right on the pin — making it easier for pinners to find and save stories that matter to them. There's also a bigger link back to the source, so pinners can easily make their way back to your site to keep reading.
Article pins can help businesses reach new audiences, get more traffic and extend the life of their content since pins remain clickworthy and discoverable long after they're published.