Wired asked more than 2,600 users of iPhone 3Gs around the world to test their downloaded speed and concluded that data speed problems have more to with the carrier networks than with Apple’s phone.

The purpose of the study was to gain a general geographic idea of where the iPhone 3G was performing best and worst. The performance data was plotted on a map of the Earth.

The key findings were as follows:

• Testers in Australia had the slowest download speeds, about 759 Kbs.
• Testers in Germany and the Netherlands had the best, averaging 2.0 Mbps.
• In major metropolitan areas in the U.S., it appears that 3G towers are overloaded, resulting in poor performance.

Wired also reported on the performance of various carriers and found that T-Mobile, in Europe had the best download speeds averaging 1,822 Kbps. AT&T in the U.S. was tied for third place, averaging 990 Kbps.

The general conclusion was that the iPhone 3G was performing as well as any other 3G handset and that the carrier’s network performance is the key determiner of the download speeds.

In a related story, testing of the iPhone 3G by Bluetest indicated that the iPhone 3G’s transmitter and receiver, for the unit tested, was completely normal.