It happens all the time: you're registering a free e-mail account or making a purchase online, when up pops a wavy, multicolored word. The system asks you to retype the word - and you roll your eyes, squint a little, and transcribe. This little test is one of the most successful techniques for making sure the person trying to log on is really a human, and not a digital "bot" prying into the site.

But now, when you type that word, something else may be happening as well: You may be deciphering a word from a decaying old book, helping to transform a historic text into a new digital file.

Jessamyn West, a library technologist, points out that these tools and games - which people can sign up for voluntarily - give people a rare chance to do small nice things without leaving their desks. "I think people like feeling like they're helping," she said. "They recycle, they pick up litter, they'll pick a penny or leave a penny."

In a time when the Net seems overrun with spammers and trolls preying on our ignorance, desires, and fears, she finds it cheering to know that people are looking for ways to reward cleverness and generosity - a micro-ethics of clicks, games, and tag clouds.