> You could get a phantascopic system planted directly on your retinas,

> just as Bud's sound system lived on his eardrums. You could even get

> telæsthetics patched into your spinal column at various key

> vertebrae. But this was said to have its drawbacks: some concerns

> about long-term nerve damage, plus it was rumored that hackers for big

> media companies had figured out a way to get through the defenses that

> were built into such systems, and run junk advertisements in your

> peripheral vision (or even spang in the fucking middle) all the

> time—even when your eyes were closed. Bud knew a guy like that who'd

> somehow gotten infected with a meme that ran advertisements for roach

> motels, in Hindi, superimposed on the bottom right-hand corner of his

> visual field, twenty-four hours a day, until the guy whacked himself.

-- Neal Stephenson, The Diamond Age