Speculation among iPhone 4 owners has suggested that carrier AT&T have begun capping 3G upload speeds, with some users reporting a tenfold reduction in rates. The company has made no official statement as yet, but in certain areas where previously speeds in excess of 1Mbps were being recorded, now sub-100kbps rates are more likely. It's unclear whether solely iPhone 4 owners are being affected, or if all AT&T devices are seeing the same throttling.
Gizmodo points to the MacRumors forums where members have been compiling a list of affected areas. So far, NYC, Central Jersey, Boston, Orlando, Seattle, South Jersey/Philly, Columbus, Cleveland, West Houston, Phoenix, Northern Colorado, St. Paul/Minesota, Suffolk County/Long Island, Quad Cities, South Jersey, Denver, Detroit Metro, Cincinnati, Baltimore, Salt Lake City, Las Vegas, Kansas City, Fairfax and Minneapolis have all been tagged as problematic for upload speeds.