PoniesExpress - 5:45 pm on May 6, 2010 (gmt 0)
What I'm seeing may validate your theory. My homepage was suddenly dropped from the index on May 1st. I believe this is a duplicate content issue, but I'm not at all certain. We made no changes on our side, so it must be the algo change, and I doubt it's because of a penalty, because all our other pages are indexing.
Not sure what's going on yet, but I'll update when I learn more.