robho - 7:54 pm on Oct 3, 2011 (gmt 0)

Have you considered the other approach - rather than banning bots, allow only humans?

Allowing a few queries then checking the user is a human with a captcha is a fairly common approach on webmaster-targeted sites (such as for whois, speedtest, dns test, geo ip, etc).

That way, robots don't get to see much, don't get to use the API calls.