When I use my Vodafone USB stick on their UK 2G network, they silently proxy everything and compress images - it's dreadful. On 3G, they seem to let images thro

When I use my Vodafone USB stick on their UK 2G network, they silently proxy everything and compress images - it's dreadful. On 3G, they seem to let images through in their original state. They're also pretty censorious. Needless-to-say, the likes of 4chan and porn are blocked on Vodafone's cellular network. But so are Flickr, Meebo, Google Talk and a whole host of other inoffensive yet useful websites. All redirect to a page telling you that they're barred by "content control". Why can cellular operators get away with blocking stuff that other ISPs would never dream of filtering out? Why should it be any different whether I'm accessing the net through my Vodafone dongle or my ADSL line?