I have known some unusual uses for CLI
('Calling Line Identity' - where your telephone number is passed to the caller so they can see who is calling).
It is well known that Banks and credit card companies use these but the most useful I have found so far is for Dominoes pizza in London and Homerun pizza in the Isle of Man as this allows them to remember my previous order, automatically know the delivery address and, in some cases, even authorise payment from a credit card.
Just the sort of thing needed after a heavy night on the ale, a dose of the 'munchies' and access to a telephone!
However, the latest unusual one was when I called one of the local radio stations today to answer a competition. After a few rings, the presenter answered with 'Hello Rob'. Whilst I wont go into my usual speech here about my proper name of Robert, it did throw me that he knew my name & I asked him how he did know it. He simply said that "..it comes up on the screen" so, at some point when I have rung in previously, someone has added the detail to their database.
Not sure if I think that's a good idea or not - could be used to filter potential competition winners and I think the 'entertainment' industry has had enough bad press over 'fixed' competitions.