Just a couple of small points
If as said at the top of the list by AC, the future of telecommunications is VoIP, who is going to install all the wires and maintain them? Without the wires (cable excepted) you ain't got no internet kid!
Lots of customer 'service' centres already use VoIP for most of their communications. I too have a couple of VoIP lines for various purposes, but I retain a land line and its number because I couldn't have the others without it!
An argument could be made for using mobile internet -- I use the Mobile Business one from Orange, which is very good, but it is not as fast as my connection to Be (up to 24meg), where I get around 10 meg. I also run a VoiP line in my MacBookPro when on the move and I agree that it is very useful indeed. I also have a mobile phone with two lines (I think you can only get two lines from Orange, the others don't do that) --- it would be an iPhone but only O2 can retail those and I prefer Orange ---- hmmmm ---- there is a rumour ..... we need to wait and see!
As for the security, VoIP breaks messages into small packets which travel any which way to their destination where they are reassembled. That makes it very hard for big brother to listen in. But, what's to stop you scrambling your normal phone calls? I mean between places where you want to talk in private and its none of big brother's business. It's illegal to scramble a private phone line in the UK (as far as I understand), but in this day and age, we merely need to scramble the 'message' before it enters the phone line --- then it looks like data --- and (don't quote me) I think THAT might be legal, because we have not attached a 'scrambler' to the phone line. I suppose it depends on how paranoid you are --- maybe you shut the windows before answering the phone ! hahahahaha