The Guardian recently ran feature on car sharing schemes, including the scheme I use: Streetcar ('The caring, sharing way to drive' Miles Brignall, Guardian Money, November 25, 2006). The piece indirectly observes the illogical ruling that drivers in such schemes effectively pay the full Congestion Charge.
The Congestion Charge was originally intended to discourage people from driving in central London during the busiest periods. One might imagine that Transport for London, which introduced it, would want to encourage one possible alternative: to not have a car, commute to work, and use a car share when you really need personal transport.
In fact, not only are car club members not exempt from the Charge, those living within the Congestion Charge zone gain no benefit from the 'Residents' discount' if they drive infrequently -- which is the typical behaviour of people in car sharing schemes. According to TfL's bizarre logic, "vehicles used under such schemes still contribute to traffic congestion". So, one less reason to avoid car ownership or limit one's journeys.
See my article in spiked Environment London: still stuck in a jam Nico Macdonald, spiked, 19 March 2007 in which I argue that, four years on, the Congestion Charge hasn't got Londoners moving faster, and that it represents a failure of policy and a failure of imagination. [Documented on my site.]