Powerful stuff @jreighley. The only thing that I can say right now is a similar to @Seneca’s answer in his Vault routing burden thread. This requires a critical mass of users.
What I’m thinking about is the actual interaction ecosphere that APPs will normalize. I forsee APPs PUTting a lot of small bits of information onto the network on behalf of the user. Either as a way for them to customize their experience with that APP privately (think config files/statistics) or publicly posting content related to that APP (think reddit/comment posts/threads).
And that’s about all the answer I can come up with at this point. There simply needs to be many PUTs generated to balance this out.
EDIT: Good points in the post above by @gohan00760 too.