Storing an ID on the phone doesn't cost anything. Transferring it to the phone could cost something, but it can easily be issued via bluetooth or infrared connection, for example from the DMV when you pass the driving test. The possibility of losing the phone is another problem though, and is the way I see it the biggest hurdle in implementing this idea.

I was thinking mobile phones when i wrote it, yes. Not everybody owns a smart phone NOW, but eventually as new models arrive the older models become cheaper. And everybody wants to have the toys that the "rich" people already have.
I definately don't think it will happen in the near future, but I truly believe it will happen someday. Perhaps towards the end of your lifetime, depending on how well you take care of yourself :)

To pay for your purchase send SMS with the word PAY followed by amount to XXXX

There will come a time when all your cards will be digital. Driving license, library card, discount cards at starbucks etc.

"The computer predicts an increase of crimes in areas A and B. Let's put some men there, and make sure the criminals spot them, and move the rest to areas C and D."

yea yea I will search for copyright on that word too :)

For the following words and characters:

first
post
copyright
patent
plus
+
apple
troll
euro
.

I could apply for some more but I figure these will generate enough money for my needs. I am not greedy and selfish.

Apple makes good, user friendly products that simply works out of the box, but they are also patent trolling corporate bullies.
Microsoft makes good, user friendly products that simply works out of the box (most of the time), but they are also patent trolling corporate bullies.
Fanbois of both camps ignore the patent trolling corporate bully part, as long as they get a product that works for them.

Yup and you can control which group can see what you publish. And people think google+ just thought of it.

1 Create different groups.

2 Add the people you don't want to chat with to one group.

3 Always appear offline to that group.