I have seen major changes for some search terms. For "Big Brand Store Widget" the big brand store had a page that has been #1 forever (appropriately) and at times has had multiple listings at the top. Earlier today I noticed the big brand store isn't listed anywhere.
About 2-3 hours ago, I noticed almost all other usual listings for this search phrase are gone (except 1) and replaced with a bunch of crap. The one that is still there is a reasonable result and is first. The second result is a store that sells a similar product but has nothing to do with the big brand store. Then there are a bunch of yelp listings for local branches of the big brand store followed by a garbage exact match domain.
Very strange. I will assume this is some major flux and far from the final result for this search phrase.