tedster - 6:28 pm on Aug 5, 2010 (gmt 0)
That is correlation, yes - but it doesn't establish causation. In fact, with Google's complex algorithm, establishing causation can be almost impossible in a lot of cases.
So it would help a lot if we get other such reports about the keyword meta tag, and at least build up a higher number of anecdotes. Even if Google is experimenting with using the meta keywords tag again, I think it's unlikely that it would be the cause of any penalties.
Have you looked at a cross-sample of meta keyword tags? What a swamp that is! Google has much better ways to determine relevance.