I put this in the head of lots of my html <meta name="robots" content="nocache,noarchive" /> for per page Google directions. In my experience, it's reliable for them. You can add a "nofollow" too to keep something out of the index entirely.

The web is not a party conversation. It's a bad analogy. Everything online is defacto recorded. Sometimes for a very short term, ie: printed to a temporary page and then the tape is erased, but it's still recorded. So the analogy becomes everyone *is* taping your conversations at a party, you just have some vague social agreement to not save the tapes.

I appreciate the fact that the CB isn't stored (and any attempts to keep it out of others' caches) but eric256 is correct--saying something in the presence of others, for example the 31 monks on the site right now, and having an expectation of privacy isn't sensible.