The interactive map linked below lists the average speed of the internet in the United States by state. A similar map in 2009 revealed the average speed in the United States to be only 4.8Mbps. This new map shows that circumstances have greatly improved in the United States in terms of internet speeds. Data for the map is from Speedtest.net. -Via Gizmodo
My guess is that Speedtest.net summarizes the number of people who went to Speedtest.net, while Akamai measures the CDN traffic, so Speedtest gets more traffic from people who just got new bandwidth and want to verify that it really is zippy fast.