Remember AmEx's announcement early this year that cardholders could now use membership rewards points to pay their taxes? Since it's always annoyed me that we can't pay taxes with a credit card for free, I, for one, was excited when I heard there was a new option for paying taxes online. That is, until I dug a little deeper into the conversion rate and realized what a waste it would be to drop 200 rewards points for every $1 in taxes due. That's 400,000 points for a $2,000 tax bill—ridiculous!