Google started the Nexus unlocked Android superphone phenomenon in early January 2010. The Nexus One, made by HTC, was designed to showcase Android on very high end hardware at a time when most carriers were offering middle of the road devices. Google also intended the Nexus One as a platform where developers and enthusiasts could get the latest OS without waiting for carrier certifications and the delays those cause. Lastly, Google sold the Nexus direct to consumers and developers on the web-- the phone was unlocked and you couldn't get it at a carrier's store or from other retailers. That last part didn't work so well in the US where customers expect contract discounts (though those were available in a limited way for the first Nexus One variant on T-Mobile) and support from the carrier and manufacturer. So Google gave up on direct sales and is offering their follow-up model, the Nexus S, via Best Buy. In my experience, given the lackluster support Google provided, that's a good thing. The Nexus S is sold unlocked (regardless of whether you buy it with or without contract) but it works best on T-Mobile in the US and abroad since the phone has T-Mobile's AWS 3G bands and 2100MHz for Europe.