The network team at T-Mobile USA seems to be in the middle of an identity crisis. They know if they want to make it any longer in the highly competitive US market it will all be about data, which is something T-Mobile has sorely lacked in. As of today, their 3G network isn't really up and running completely while Sprint is launching more 4G markets every few months. T-Mobile has taken notice of this and started talks with Clearwire.
While you may not know the name you have most likely seen commercials for their work: Sprint's WiMax network. WiMax is the CDMA evolution into 4G which was a natural progression for Sprint seeing as their network has been CDMA since it was built. T-Mobile, on the other hand, is a GSM network which has its own evolution, called LTE. It would appear T-Mobile is considering switching teams, but in the opposite direction as Verizon, who is making the 4G switch from CDMA to LTE.