You know the kind. Goto any speedtest site and somehow you're getting exactly 12MB down, 3MB up, but it never really seems to add up that way anywhere else. Even to my own office, which I know has an extra 100MB to burst, yet somehow my downloads from the data-center across town are more likely to end up in the 3MB range 99% of the time.
Speedtest was originally made to test the 'last mile', assuming your ISP's connections to the rest of the world is always faster than that. In most cases that is true, but it is possible it isn't in your area.
As a particular clear example of that, here's my little write up on Speedtest.net usage in Rwanda: http://blog.nyaruka.com/stuff-0
We've seen this with unlimited data plans with the cable ISPs; they're not really unlimited.
To me, it's similar to having a traditional credit card versus one with no pre-set spending limit. Which would you rather have? The latter has a limit, you just don't know what it is until you hit it.
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[1] http://mozy.com/terms/ "....excessive use of the Service, which means usage over a given period far exceeds the average level of usage by users of the Service generally..."
That suggests an interesting business model where: we sell everyone on 'Unlimited', then we wait to see who is the most egregious customer, and drop off the ones on the top of the pyramid (and keep the revenue positive customers).
Reminds me of how the cellular operators used to be towards roaming: sure, you can roam, just don't do it so much that we cancel your contract.
You can still freeload up and until you hit the limit.