I believe that the Speedtest results are manipulated by the ISP's. You will be lucky if in reality you get a quarter of what shows up in speedtest results, and definitely far lower for what any ISP advertises.
It would work something like this:
It is very simple for the ISP's to turn off all throttling and give priority to all speedtest.net traffic, while having any other traffic resort to their regular throttled speeds. That way all the speedtest results show up as high as possible, convincing you that are actually receiving in reality what you paid for.
For example, let's say I paid for, and received cable that is capable of 100mbps. Obviously it will be impossible to achieve those exact speeds with the many roadblocks that slow it down. So I'll guess that the realistic speed will be around 80mbps. The ISPs throttle your internet to a meager 25Mbps, though when you do a speedtest, they'll prioritize and de-throttle your connection to show you results close to 80mbps.
Even worse, even the regular throttled speeds you enjoy while web browsing are sometimes throttled even further while downloading torrents or streaming videos, or basically doing anything the ISP doesn't like.
Doesn't this sound very plausible?
