(can someone explain this more?--)
"could be done by having read-only links be more random and then not require pad passwords (with ability to expire/remove them)"
I beleive the code exists and what's missing is to make the readonly link visible.
Further explanation by jefferai@foundation meeting 3:
This exists. Go to the time-slider view of a pad. In that view, there is a link near the top-right to "Readonly version of this pad".
This functionality is also actively used and promoted in my twitterstyle-tags patch.