I personally find that Pinterest allows me to give the person who's work I'm viewing credit. Before I had no way to really remember who's work it was that inspired what I was working on, and I wasn't able to give them proper credit. When you pin, it's basically posting a link to the site where the person posted the information.
Would you also consider it a copyright infringement for me to blog about a quilt that inspired me and put a link to the person's work for others to follow and see?