To transportation planners, mobility and accessibility are precise terms that mean different things. Mobility is the ability to travel, and accessibility includes the cost of travel. While these two concepts share many characteristics, increases in mobility do not necessarily lead to increases in accessibility. One major question for public policy is what level of mobility and accessibility should people be guaranteed.
In Coy, Alabama, this is a major concern. In today's LA Times an article provides some details about how the price of gas is affecting the residents. Since people live in a rural town, they are auto dependent for their mobility. Since they are also poor, they have a hard time with the high price of gas.
This is an extreme example of isolation, but if that town is to survive, some level of mobility (and access) needs to be maintained. We can't let people become splintered away from society because they can't afford the very modest costs of local travel. However, if small town residents were given lifeline fuel credits, for instance, an incentive for other people who can afford to travel to move to the town is created. That's bad, too.
This is a difficult question, but the larger issue of rights to mobility and access will be a major concern for public policy in the near future.