Which web services should ISPs give maximum QoS to?

Just a quick cynical thought here.....

...I'm doing a bunch of research at the moment on whether there are particular Internet services that broadband operators (fixed or mobile) might choose to prioritise, or indeed deprioritise/throttle. I'm especially interested in whether there's any real-world business models where "upstream" service providers actually pay cold hard cash to the access network owner to get extra QoS / bandwidth guarantees.

It's just struck me that there's certainly one group of websites that it's worth ISPs prioritising if at all possible, even if they don't actually charge for it: speed-testing services.

I wonder if any of the DPI boxes have been programmed to recognise "speedtest.net" or similar, and make sure that there's as much optimisation as possible thrown at that particular HTTP session?

I'm reminded of some car companies which (rumour has it) only give reviewers the most "special" examples of their new vehicles to test....