Right now, the default for the # of AZs is "as many as you can get", which leads to consistent problems in us-east-1 (because it has so many AZs): I can't start a default VPC because I run out of EIPs.

What's worse, code that runs fine in one region fails to start in us-east-1 because of this, which is worse. You think you've tested something, but then it doesn't work.

Since there's diminishing returns of additional AZs after the 3rd, why not default to 3? (But let users raise the number, obviously, if they really want to).

Also, we should probably make it possible to define an offset as well, so that you can have two VPCs spread over all 6 AZs (one a-b-c, the other d-e-f).