You can test on many different servers, I tested to a server in virginia since I assume it would be a reasonable proxy to ec2 us-east bandwidth.
Netflix hosts their video servers much closer than ec2's us-east...
The list of speedtest.net servers is public and I don't doubt that Comcast uses it to drive traffic shaping decisions. Speed tests are meaningless except to establish an upper bound on last mile speed. They are not representative of bandwidth to real services like Netflix, YouTube, Dropbox, Steam, etc.
I can't argue with that. I just checked actual scp speed to and from ec2 and I'm getting slower downloads then uploads right now. At 7PM my time. 6.3mbps up, 4.5mbps down.
speedtest.net shows those exact speeds now as well. That's nice, 80% of bandwidth going away in a few hours :-)
Doesn't the 20-25Mbps speedtest focus on "speed boost" where Comcast gooses the speeds for initial connections (so web page loads are faster, but sustained downloads are slower)?
I am pretty sure nothing is streamed off of AWS - possibly Cloudfrount , but based on what I know of Netflix use L3 and Akamai heavily.