Different groups have different estimates, and most don't separate mobile Internet users from those accessing the Web from a computer, even though the two groups face different choices of browsers.

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Like any computer system, Paradiso says X-Reality implementations would require different levels of access based on verifying users' identities.

FORBES: Breakthroughs

Many of us already use what is called 'virtualisation' technology to run different operating systems at the same time, like the Mac users who also have Windows on their computer.

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On Facebook, for example, two-factor authentication is triggered when users try to log in in an unexpected way, such as from a computer in a different country.

BBC: Technology

Such technologies could allow users to watch shows they have saved or purchased on two different devices, like a TV and a computer, without having to buy or record the shows twice.

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