Rosalind - 8:56 pm on Dec 28, 2011 (gmt 0)
Have you used the Bing Webmaster Tools specifically designed to allow you to control the rate at which we crawl your website?
That's what Crawl-Delay is for. And what's better, webmasters don't have to sign up to your proprietary site to be able to use it. Imagine the chaos if every SE had its own webmaster section that people had to have heard of in order to sign up to in order to fix simple stuff like Crawl-Delay!