People in countries where the device isn't on sale yet. There are two issues with this:

1. If someone in the UK (for example) has an iPad out in public, and makes someone else interested in buying it, their only route is to also try and import one. Thus creating a market for people in the US to buy them and sell to people wanting them in the UK. Most likely jacking up the cost along the way and taking a unit out of the market where Apple is trying to keep them in stock. Apple would rather have the units available in their stores so when someone wants one, they can walk in and buy it.

2. Certifications. Due to the WiFi and 3G hardware, the device has to be certified by a lot of different organizations. 802.11 in the 5ghz range is particularly tricky right now, with countries widely varying on what channels can be used. 802.11 in the 2.4 ghz range used to be similar.

As for the "for life" thing, that seems to be something added by the clueless Apple Store drones, and not a corporate policy. It will change once they can meet the currently high levels of demand.