The problem with the Episcopal Church in America is that nobody's in charge. The Presiding Bishop doesn't really have that much power over the other bishops, so when one really goes off the rails (and into the pond) like Spong, there's not much that can be done. A letter of censure would be about it, I don't think he can be defrocked, or at least it's almost impossible.
I look to my local bishop (he's a new man and I'm reserving judgment for the moment until I learn more about him) and my rector. At the moment, they seem to be doing all right, but if the national church takes a position in favor of non-traditional "marriage" (or the ordination of practicing homosexuals), we're gone.