While I wish I could comment in depth on the subject, I will add Rio de Janeiro to the list. Here, we have orange Itaú (a bank that sponsors the program) bicycles throughout the city and they're quite popular. You sign up online and they have some sort of integration with your smartphone. I was recently informed they are R$10 (US$5) per month on a monthly plan. The downside is, also from what I've heard, you have to dock them every hour and take another bike.

Here's a picture of them

http://www.bikehype.com.br/wp-content/uploads/2012/02/alugue...

and a supporting article

http://www.smartplanet.com/blog/global-observer/take-two-for...