Ok, let's turn this on it's head a little bit.
The main concern here seems to be the use of the internet by "criminals".
How many "criminals" do you think use mobile telephones?
Do you think it's a coincidence that the sale, in the UK, of the pre-paid non-traceable mobile phones has gone through the roof over the past couple of years?
No it's down the the fact they they are one of the best tools for the budding crime lord to use.
GSM digital encryption prevents the casual evesdropper from hearing the calls palace on the network. The fact that you can buy the handsets from a petrol station forcort with out having to produce any ID or have a billing address makes the users untraceable.
OK, the point I'm trying to make here is - Would you want the secret service or whoever to monitor every mobile telephone conversation, including yours and mine, just incase it picks up a conversation about a big crack deal?