[the urban politician]

^ Plus I'm sure the city has a reasonable concern that the bikes could really undergo a lot of wear and tear in the winter months, which perhaps would increase costs.

One solution I can think of is to "winterize" the entire system with more treaded tires with spikes (as discussed in the cycling thread by Steely) just before winter, and then "dewinterizing" as spring arrives. An alternative is to have an extra fleet of "winterized" bikes available during that time of year (think, extra tread and even heated seats!) that people can use for a slightly extra cost.

On another note, think just how awesome it would be if you could use your CTA card as your "bike sharing" card as well. Combine that with Metra, and boy mobility would be just that much enhanced. Chicago really needs to unify its transportation system. I also imagine a scenario where, like "bus tracker" you can use "bike tracker" on your smartphone to determine how many available bikes there are at a given station.