grarpamp[at]gmail.com:
CloudFlare throws up a captcha with a comment field
for a message that goes to the site owner.
So all Tor users fill in the comment, with
perhaps even the same generic message...
"Stop blocking us."
Which naturally makes site inquire their logs to see who
"us" is, and as byproduct discovers that your clickstream
was actually legit and not whatever they thought they were
blocking.
or
"I'm a Tor user, stop blocking me."
Which is more informative and personal.
It would seem someone here could write
FF/TBB greasemonkey for those too lazy to fill in
that field.