Judging from the leading question that titles this thread and the link to your blog, which is a promotional web site for a private bike rental entity I would conjecture there is a certain amount of bias behind your query.
I hate to run counter to the "unwanted child" label but I have used the bike share in London, watched as the Citibikes were rolled out in NYC last summer and live in Boston, where the Hubway bikes are moving into their third year. My observation has been that all three are highly successful. I say this as someone who managed a bike shop that did a thriving rental business in a summer tourist destination.
Bike share is here to stay because it works and satisfies a need that standard private rentals just can't compete with adequately.