I just realised the extent to which UK mobile networks bugger about with your internet connection on your phone.
I had noticed aggressive image compression on certain sites – the Youtube logo looks pretty terrible, for example – but I had assumed that it was done at the website and appplied selectively to IP ranges or browser User-Agents that are likely to be mobile phones. While this does sometimes happen, it seems that both O2 and T-Mobile (and probably others) also dynamically recompress images coming across their network.
This is:
a: Annoying, given that I’d rather see the real internet on my phone – after all this is the point of having a fast HSDPA connection and a big screen
b: Intrusive, given that you don’t ask for it, they simply do it.
Of course, dynamic compression is not an unknown phenomenon – Opera’s mobile browsers and the BlackBerry Internet Service have done it for some time, but in those cases you expect it, and to some extent choose it. There’s no reason for it to be the default on the cell network.
Evidence:
A picture of an unreleased phone, downloaded via the plain-ol’ Internet:
O2′s version of it:
T-Mobile’s version of it (even worse):
At least the O2 version is at full size – the T-Mobile one is ridiculous. Of course, if you’re viewing this via either of these networks, all of the pictures probably look equally terrible 
I’m going to try to find out if it’s possible to switch this off. It’s obviously aimed at saving them bandwidth, but it serves no purpose for the customer.