It's a longstanding tradition: On historic occasions, Google gives over its homepage to major figures in art, history, and literature. Today, it's the turn of Mark Twain, Samuel Clemens, the famous American novelist.

In Google's stomping grounds of Silicon Valley, Twain is best known not for his written works but for the business model he inspired—the Tom Sawyer, as it's known, after the hero of the eponymous novel, who somehow persuaded his friends to paint a fence for him.

That's the scene that popped up on Google.com Wednesday, drawing some praise from Mark Twain fans.

The Tom Sawyer model has brought good things to us—for example, YouTube, where people voluntarily post amazing videos, some of which are actually their own work. That activity, in turn, builds enormous value for Google, which bought YouTube for $1.65 billion in 2006.

Creators of content grump ad nauseam about how Google builds its search results on the strength of their content—not that they complain about the vast amount of traffic Google directs their way, mind you.

Then there's an army of bloggers—and spammers—who create Web pages largely in the hopes of them appearing somewhere, anywhere in Google's search results.

So Google has done well off of being the Tom Sawyer of the online world. And it has done some good for the world, too, in the work it's cajoled from others.

I'm just not sure it's a wise idea to rub everyone's face in the paint after they're done doing the work.