Besides marrying to scam companies (such as 3721), ratting out political dissident even when they don't have to, Yahoo just added a new entry on the list of why they are inferior to any decent business, including although not limited to, Google et al.
According to Boingboing, Google rejected the Department of Justice's subpoena to expose its user search record, while Yahoo said yes. Although what DoJ had requested were seemingly randomized data with no direct references to any personal profile, these kind of movements are of great concern because 1) It sets a dangerous precedent full of potential of imaginations, especially when these data are derived from actual personal information search engines hold; 2) It's hard to tell what information data mining techniques can provide today or tomorrow on these kind of data; 3) An immediate effect could be that DoJ isolates a particular attention-drawing person or group of persons, and demands identifiable information on legitimate causes. John Shinal of Market Watch wrote, I'm not sure what's more troubling -- the fact that the U.S. government wanted to get its hands on the Internet search results of millions of its citizens, or that some of the leading search firms were so quick to provide the data.
More information at Danny Sullvin's Search Engine Watch.