Once worked on a whois scraping project and ran into a bunch of issues.<p>One particularly fun story is how we might have broken a whois server. It was the country TLD server for some West African nation, I think Senegal but I'm not sure. We hit their server with like a hundred queries in rapid succession (to test what rate limiting approach they used) and requests started hanging. We switched IP addresses ... and still requests were hanging. We tried multiple IP addresses in totally different networks, all of them hung or timed out, even for a single request. A day later we retried and all of a sudden it started working again! From that point on we made sure to never do more than a couple requests a second to that particular domain.<p>Also, any queries to one cc TLD (either Egypt or Ukraine, can't remember which) just returned "we don't provide information in whois requests" or something to that effect.<p>GoDaddy didn't do traditional rate limiting. If you exceeded whatever their limit was they didn't just return an error message, they would blacklist your IP and for any query say "visit our website for information", and their website gated things behind a captcha.