Yesterday we reported that MSNBot failed some reverse DNS tests. In short, if you did a reverse DNS lookup on the IP addresses of their spiders, it would not resolve to search.live.com. The big issue with this is that Webmasters who have set their servers to block rogue spiders that don't pass reverse DNS tests, would be blocking a legitimate MSNBot and possibly notice a drop in traffic from Live Search.
MSNDude has replied to the WebmasterWorld thread confirming the issue and promising to resolve the issue as soon as possible.
Thanks Shurik for detecting this configuration issue on few servers, we will fix that.
Again, this can be a very serious issue for some sites and should be taken seriously by both webmasters and Microsoft.
Forum discussion at WebmasterWorld.