The local SEOs are buzzing big time right now. It seems like over the past few days, Google has done a major algorithmic change that has shifted how the local results rank in both Google Maps and the local packs in web search.
It is believed that the Google Maps Googlebomb fix led to this and I actually said then "expect the traffic change some for many local businesses in the near future."
It seems to be related, although Mozcast features shows the shift on the 15th. I cannot find any serious discussion around changes in local results as early as the 15th, only shortly after the Google apology after the 22nd.
The Local Search Forums has tons of local SEO experts documenting the change. You have Mike Blumenthal calling the location results screwy and the forums are simply lighting up around this.
I find it hard to believe it is not around the change Google made for the Google Maps bomb.
It seems like something went wrong with location detection and ranking of local results. It is almost believed to be a bug with Google's location detection systems. But it is awkwardly around the same time of the Googlebomb fix.
I'll try to find out more from the source, Google.
Forum discussion at Local Search Forums.