Kedrosky has a post up that says 1 in 18 households in the US are now "millionaires".
It recalls British publishing billionaire Felix Dennis' new classification of wealth:
|£1m-£2m||The comfortable poor|
|£5m-£15m||The comfortably wealthy|
|£40m-£75m||The comfortably rich|
Beyond that come the super rich and the filthy rich...
Note that figures are in british pounds, so it's roughly $2-4M in USD to be comfortably poor.