My bookmarks keep falling out of the book

I had forty scraps of paper marking the important pages. Then I sneezed. — Law student, 1976

In 1968 a 3M chemist named Spencer Silver set out to make a strong glue and made a weak one. He spent years showing it around anyway. Proud of it. Art Fry, a colleague whose bookmarks kept falling out of his church hymnal, figured out what it was for. 3M handed out free pads in Boise, Idaho, and 90% of the people who tried them said they'd buy. A glue nobody had a use for, and nine in ten wanted the note. Sometimes the mistake is the product.

Still bugs us: sticky notes fall off too, and always seem to land behind the desk.