I'm not a fan of percentage based fee's. The fee's are paying for the cost of doing the work to process the transaction. It doesn't cost, computer power wise, anymore to process a $.01 transaction or a $1 million dollar transaction.
I think there may be a better answer to micropayments, other than percentage based fees. Percentage based fee's are really a legacy form of tax, and we should look at some alternative and innovative forms of fees while we are still young.