That's funny because so far every proof-of-stake proposal I've seen says "Minimum X (large) coins and peasants get to fill out napkin size complaint form".
There are 2 proposals (see
https://en.bitcoin.it/wiki/Proof_of_Stake, also linked in the OP) and none of them say anything about a minimum. The "minimum" that may be needed in practice is on the order of magnitude of dollars.
I think you might be confused with the SolidCoin system.