Better than Orange's £3 per meg scam
Orange *still* by default charge you a standard per-meg charge (now £3 per meg) unless you say so otherwise, and it's not hard with many phones these days to download quite a lot of data without realising (e.g using a map application like Google Maps or Nokia Maps).
In fact Orange offer a daily capped rate for £0 extra on your monthly bill... but they don't advertise it and don't give you it by default.
Worse than that (as I have found), even if you change to daily capped, they seem to ignore the request and continue to charge you at £3 per meg. Now I have to fight some £100 worth of data charges over the last 6 months for around 20 meg of data used! (although some was overseas... at £8 per meg!!!!).
Sadly even though I have WiFi on my phone, finding reliable hotspots is near impossible as is finding any that have decent PAYG payment (i.e. pay just for what you use, not pay £7 for an hour's access whether you use it or not!).