How local is a local church?

How close is a "local" church? What is the relative role of proximity in determining church membership? (Not just descriptively, but normatively: i.e. what should it be?) How much commuting is it reasonable or responsible to encourage and model?

Since being baptised, I've been a member of four different churches and each was within walking distance of my residence at the time (this doesn't mean I have always walked every week). My most frustrating experience of fellowship was (unsurprisingly) when this distance was greatest, making hospitality and mid-week meetings much more difficult.

What are the difficulties that arise with integrating members from further afield? What experiences, insights or prophetic words do readers have on this topic? Has anyone ever encouraged a fellow congregation member (or prospective member) to find a church closer to home? (Or a home closer to church?) Do any churches have centrally organised car-pooling? Is anyone part of a congregation where more than half your members walk to church?
Image by JKS of me preaching in a church (through an interpreter) where 100% of the members walk.