They want to charge more for data?
Is that even possible? £15 a month for 3GB data allowance isn't what I would call generous. If they can't handle the traffic then why offer the service at such speeds that people can happily torrent large files all day. How much are they planning to charge for a bittorrent app then? Say the average person downloads 5 movies a month and a few music albums, that's getting perilously close to a £15 a month sub just for that at current data prices. Or what about an iPlayer app?
You can't charge a flat rate for a Youtube app either, what about all the people who exclusively watch SD/HD videos? Their usage patterns would be vastly different and would require a different charge. How long are people's phone bills going to be listing all the apps they are "subscribed to"?
How long before we are back to "oh that app uses some data? That'll be one arm and one leg please."