lucy24 - 4:51 am on Feb 5, 2013 (gmt 0)
I started returning a 404 to Googlebot
Please say that's a typo for 403. Give google a 404 and you'll never see the last of them. (Google, unlike bing, distinguishes between 404 and 410.)
And, er, it's a quibble admittedly, but the adverb "officially" modifies the verb "become", not the adjective "illegal" ;) You'd have to really contort the sentence to read it a different way.
I don't think there's an internationally recognized standard directory of scrapers-- legal or otherwise-- though.