SkimLinks is really handy if you have the right kind of site - something fairly high-quality, not controversial, not adult, and full of products. If I'm going to do a lot of business with a single merchant, I prefer to keep the relationship direct (and negotiate a higher payout than what you'd get through SkimLinks), but in cases where you have product links going all over the place or user-generated content, it's a huge timesaver.
Funny story about Pinterest and affiliates - I saw Ben Silbermann talking last week at a local meetup and some guy asks, "So I was reading an article on a site called Blogspot last week - you may have seen it - and some guy was teaching these nefarious individuals how to make money on Pinterest by putting their special internet marketing links on the site. How do you think that will influence your ability to monetize the site?"
Silbermann's answer was something to the effect of, "Well the beauty of Pinterest is that users only see things they like. If they don't like marketing and spam, they won't see it."
Is it possible that Pinterest is as clueless about affiliate marketers as most affiliates are about Pinterest? He didn't seem to grasp the idea that affiliates wouldn't be pinning things ABOUT spam and internet marketing...but that they'd be using their own affiliate links on seemingly normal pins.
EDIT - Also, if you just want the ability to turn certain words into affiliate links, you can use Pretty Link Pro - It's only good for Wordpress, but it's super convenient and lets you use your own links/manage your own relationships.