Matt Cutts responded to the Google anomaly we reported last week, where Google was displaying a different site's information from the same shared server. In short, two sites are hosted on the same server and same IP address. When conducting a search that should have brought up Site A, Site B was coming up in the SERPs.
The issue was technically not on Google's side, as Matt explained. The server folks that set up the server set up the virtual hosting configuration incorrectly. So why wasn't it an issue on Yahoo, MSN or Ask.com? Matt explains that Google uses "persistent connections to a webserver via a Keep-Alive header" that allows Google to use one single connection for all the sites on one server, thus taking up less server resources for Google and the Webmaster's server.