I have my reasons for still liking paper books once in a while, but those reasons are slowing vanishing, and the benefits of electronic books are accumulating.
I read Pinker's mammoth The Better Angels of Our Nature: Why Violence Has Declined on the Kindle app on my iPad. I was grateful not to have to read the enormous paper version of the book. It was a fascinating read, and I made lots of notes and highlights on my Kindle app. (You can make notes and highlights with a Kindle device too.)
Whenever I finish a book, I "process" it. This means going through all the notes and highlights I made and incorporating them into the books I'm writing, the literature reviews I maintain, etc. For a book the size of Pinker's, this would take a few hours.
However, on the Kindle those notes and highlights are saved automatically.
For Pinker, I had 164 highlighted passages, and a few notes. All of them were on this webpage for me to copy and paste into a googledoc. I still have to incorporate them, but I don't have to type them in.
Added February 2013: They moved the link: https://kindle.amazon.com/your_highlights
Pictured: A bikeshare. Bikeshares tend to fail, I've heard, when helmet laws are in place.