Meh, Mike proposes terrible ideas all the time. Predictably it's getting shot down, and will probably sit there unmerged forever, just like his pull-req to turn the totally broken nSequence replacement back on. Heck, I'm only really replying because I'm quite fond of polishing my writing skills; it'd probably be more productive to get it merged and attack it later.
Speaking of, if you want to have some fun with dumb unauthenticated applications:
https://github.com/petertodd/bitcoin/tree/bloom-data-hiding-attack
