Your service provider will throttle your service too if they see that you are hogging bandwidth.
I recently discovered that my supposed unlimited data on my wireless broadband, which hooks up to the nearest cellphone tower (basically it operates like a cellphone), is limited. Well, the data consumption is. For a while I thought the service provider was throttling me. But, as it turns out, the cellphone tower that I hooked up with was throttling my connection. Not only that but they eventually booted my router completely. Mind you, I was living in the suburbs of Chicago during this fiasco, but after I moved to the city, everything has been smooth sailing. So I have a third party involved in the functioning of my broadband connection. I'm not necessarily pissed about this, but it does add to a bit of frustration when third parties get involved.
The service isn't fast (3mBps) but it's ample, and I don't have to deal with service plans or hidden fees after the initial starting date is over (that shit makes me furious).