So... I decided to change my homepage title the other day. My homepage title has not changed in years, and I've been #1 for my primary keyphrase for years.
Recently, however, I made it to page 2 for a much higher-traffic, more generic keyphrase. Since the Mayday update, I noticed I was popping in and out of the second page spot periodically -- sometimes I'd be on page 2, sometimes not in the top 100.
So I decided to try changing my title to include an exact phrase match for this new phrase, (it didn't before, it's a two-word phrase and I had both words, but with another word in between). I figured maybe that would solidify my position, maybe even move me up to page 1.
Result? Instantly removed completely from that SERP. A subpage now appears on page 9. My other rankings have not changed at all.
Does that sound like an over-optimization penalty? It's not like I'm stuffing the phrase. I have one exact match in title, and one exact match in the body text, and lots of relevant related phrases all over my site.
Has this sort of thing always happened? Could it be a clue to the new algo change?