I added my keyword to the randomizing content the other day and I went from #1 in MSN to #54. Probably a coincidence, or maybe they penalized me for keyword stuffing or something, but either way... it sucks.
I'm convinced that Old Welsh Guy was right-on with his lecture on the seo problems inherint with randomized/changing content on a home page. Like GeorgeB, I too experienced a free-fall of rankings for several of my websites. Like GeorgeB, I too had daily-changing content on these home pages. In my cases i'd estimate that 70% of the content changed from day-to-day. After reading OWG's comments in this thread I made some of the recommended changes to my home pages. My sites have now come back up on the serps. I'll see in the next few days/weeks if they stick around their current rankings. I expect they will. Thanks again OWG.
Undoubtedly changing too much of your content is not going to have a positive impact. How the hell are the SEs meant to know what your site is about if the majority of your content is changing daily...