We reported about a possible Google update around February 13th and I do believe there was something rather large on that date - but now there is more chatter about a possible update early this week, this past Sunday and Monday at Google.
The ongoing WebmasterWorld thread has a lot of discussion from webmasters about a possible update. Here are some recent comments:
Has anybody noticed a drop in their rankings yesterday or today specifically?
Yes, but could just be the continual state of flux I see. Though Mozcast reports activity, so you may be on to something.
Another update happened 100%. Expect a bumpy few days. If you recover, great. If not nothing you can do. Check your money terms, see if the organics have all but disappeared below ads & image results. My money is they have used Google Shopping data to spot the money terms. If your site relies on that term kiss goodbye to organic traffic.
Did you notice ranking changes and referral changes from Google earlier this week?
Forum discussion at WebmasterWorld.