Since all this has been discussed many times, let's keep it simple.
When you are testing on TWC's network, you'll get the best results. When you go outside that, you are testing how good and big are the connections from TWC's network to other networks.
Some have tried to make a case that the ISP is not delivering the speed, but then we would be repeating prior discussions.
Bob
I went to timewarnercable.com, go to their speed test and it says I'm at 30mbps.
Other speed test sites (Below) show me at 2/3 less speed. I am paying for 30 mbps, I am not sure how 4 other test are not close to what TWC shows.
Am I getting what Im paying for?????
http://www.speedtest.net/ says 9.33
http://www.att.com/speedtest/ says 9.61
http://www.internetfrog.com/mypc/speedtest/ says 6.17
http://www.speakeasy.net/speedtest/ says 10.03

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic