Are these the effects of Google Penguin 2.1 update or of the Google hummingbird?
Google are definitely presenting it as if it's down to Penguin 2.1, and the general IM media outfit seems to be buying it wholesale right now. They're all broadly sticking to the "Hummingbird has no meaningful impact on search results, so it must be Penguin 2.1".
I'm not buying it though. If you stop looking at what 2.1 has done to your sites, and instead look at the trend in the results being returned by the search page, you'll see that the quality (as measured by Google) of the page one returns for most niches now seems to be occupied by high authority, high quality, high utility and PRECISE brands and sites, with very little in the way of churn and burn and low quality representation. I believe Google have said that Hummingbird will lead to more precise, higher quality and far more useful search results. So that, to me, suggests that this has very little to do with Penguin 2.1 (which I'm guessing was just a data refresh + possible tweaks to make it compatible with the new functionality they've almost certainly added to Hummingbird), and more to do with Hummingbird.
That's just speculation though.
I'm not suggesting that Penguin 2.1 isn't responsible in part for what we're seeing. I don't think it's entirely, or indeed majorly responsible for the changes we're seeing however. This isn't just a case of a typical Penguin update taking out sites that have used particularly obnoxious campaign strategies and moving everyone else around a little bit. Certainly the data refresh will have had that impact, but that impact is being overshadowed by the very broad and colourful changes in the types of sites we're starting to see on page 1.
Also, I'm guessing the upcoming Panda data refresh will see all of those weird sites we're seeing in certain niches relegated and replaced by Hummingbird's "precise and valuable" search results.