At the moment there's an argument going on between various operators of internet connections and users of said connections.  The operators are "shaping" traffic (i.e. blocking and limiting it) in order to keep their bandwidth bills down and threatening to charge the sources of large bandwidth drains for access to their networks.  And by "sources" they they mean Google Video, YouTube and the other places that produce the stuff that users are downloading.

The reason for this is simple - they're terrified to charge users for the bandwidth they use.  UK ISPs aren't so bad - most of them have been charging for the amount people download (over a set minimum) for a while now, but US ISPs seem to be so terrified that doing so will cause an outcry that they've decided it's easier for them to go after the suppliers of the goods that attracted users to the internet in the first place.

The answer is, of course, for both suppliers and customers to realise that you get nothing for free, and if you want to download lots of shiny things then you're going to have to pay for it, because the people you're using for your connection sure as hell are.