Perhaps Microsoft is gearing up for combat in the web search index size wars. From August stats for e-scribe.com:
12.77% msnbot/1.0 (+http://search.msn.com/msnbot.htm) 3.61% Googlebot/2.1 (+http://www.google.com/bot.html) 3.34% Yahoo! Slurp
So 12.77% of the domain’s hits for August came from MSNbot. When I drill down into the detail, it looks like the bot has a particular affinity for RSS feeds.