One of the sites I report on got hit by Penguin last week. I believe it was largely because of near-duplicate content they have been using, copied from one of their other sites (I had been warning them!).
In webmaster tools the site had normal crawl rates of around 500-1500 pages per day. At the start of April crawl rates increased over two weeks then jumped sharply to around 200,000 pages per day.
Has anyone else who's had a Penguin penalty noticed crawl rates like this?