shameful-In my experience (writing the checks, not winning them unfortunately) USATF allows you to file for membership if you're in the money at a race and aren't a member beforehand. Not sure if they allow this everywhere, or if Championship races are held to a different standard, but for the marathon I work this is absolutely the case. I can tell you that one of the plusses from a race director standpoint is that USATF will handle the IRS paperwork at the end of the year. If you make over $600 prize money at a race you're going to need to get a 1099 tax form at the end of the year (is it still $600?). Since most race directors aren't in the accounting game this is a decent ancillary service that USATF provides.
I respect Carpenter's principals, have read a fair amount about why he believes what he believes and I think he's got a lot of good points. The problem is that until mountain running/ultras break away from USATF and form their own governing body they're stuck with USATF's rules and administration. In a lot of cases they also receive the benefit of USATF's insurance policies, which cannot be understated. Without insurance you're never going to be able to have any kind of large scale or high level organized races. Like it or not you want to play the game you got to pay the price.
In this case, from the little I've read, I feel that Carpenter is saying a lot about his principals. I'm sure he could use the $1000, but with his sponsors and lifestyle it's not like he's not going to be able to eat by taking a stand for what he believes.