Gizmodo is reporting that AT&T is putting a cap on upload speeds that's been mainly noticeable in the new iPhone 4. AT&T hasn't released an official statement, but recently there's numerous reports coming in that upload speeds are now capped at 100kbps, which is 1/10th of what Gizmodo reportedly saw earlier. It also appears that these limits are only specified to certain places in the United States -- mainly big cities.

As you can see from a screenshot provided by BGR below, recent upload speeds have been dramatically decreased:

The following places have been reportedly affected by these data caps. AT&T should be releasing an official statement on the matter shortly. Update: AT&T's statement

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, Minneapolis