Pinterest gets collaborative with a new messaging feature. Last year, the company added the option to "Send a Pin" to friends from both Pinterest as well as sites with enabled pin widgets. Pinterest product peeps noticed pinners were turning their share notifications into message threads, indicating a need for this new, more social, function. Now, users can swap pins and discuss ideas without leaving the app or website. The threads can accommodate multiple people and morph from a "Did You Know?" note to an entire brainstorm session.