With our increasing reliance on technology why do we have to carry paper visa 'stamps' in our passport instead of using some electronic system? I am assuming a passport number is linked to a visa so there has to be an electronic record which surely could be utilized?
One reason is that not every country has computerised their passport/visa system. They're coming along, but still.
In addition, not every country's system is linked together. So even if you scanned it in at one border, you can't tell that's happened at the next.
Crossing into Zambia in 2005, they opened their book to the date, drew in a line for New Zealanders, and literally crossed off 5 lines ( | | | | with a --- through the four vertical lines).
It costs a LOT of money. Some countries can't afford the investment to get all those systems built, and staff trained to use them. It's cheaper to hire some chap who can ask questions and cross off lines in a book.
So given all the different computer and paper based systems, the only way to transmit the fact that you have a visa, is to carry a piece of paper - ie, a stamp/visa.
However, it's improving. With the arrival of those smart passports with chips in them, we now have a common way of having data stored electronically and (mostly) securely. Next that needs to turn into visas.
New Zealanders arriving home (or visiting Australia) can merely walk to a barrier, scan our chipped passports, get a photo taken and walk through. British citizens arriving home can have their iris scanned, no stamp required.
So these are slowly changing, but will take time. In the meanwhile, you get to collect cool stamps! :)