Yes, we block IPs that seem to be crawlers ignoring robots.txt. We've always blocked abusive IPs, but I tightened up the blocking a few weeks ago. A lot of people were crawling HN, most of them unnecessarily because they were doing things they could have done more efficiently through HNSearch's API.

Some users may remember that the site had gotten really slow a few weeks ago. One of the reasons it's faster now is that we cracked down on crawlers.