Among the many intriguing features of Mac OS X Leopard that Apple previewed on Monday, Web Clip is the most subversive. Web Clip allows anyone to create an Apple Dashboard widget--essentially a small application--that displays a portion of any Web page.

As demonstrated, a user can select a specific area of any given Web page, such as a video feed from a Web cam, without showing any other part of the originating Web page.

The resulting widget becomes a miniature Web browser permanently pointed at the clipped page that omits everything on the page except for what the widget creator selected. For users, this is fantastic. For Web publishers, it looks a lot like ad-blocking software.Brian Croll, senior director of Mac OS X Product Marketing, contends publishers will welcome Web Clip widgets because they represent a link back to the publisher's page.

"One of the interesting parts about [Web Clip] is that it's a live Web page, so as I click on it and click through, it actually brings me back to the page," Croll says. "So we find that a lot of Web developers love to get that traffic. They actually want us to distribute a lot of ways to funnel more traffic to their sites."

Even so, Croll concedes there's the potential for people to view pages using a Web Clip they've created without ever clicking through to the source page. "There's an easy remedy for that, which is that [publishers] can always create a killer widget themselves," he says.

That may be, but given how simple Apple has made it to create a Web Clip, those inclined to frame out ads will have no trouble making their own ad-free widget.

Now it may be that this technology won't have much impact initially because Macs still represent only a small portion of the PCs in the world. But if Microsoft copies Apple as readily as Apple claims, it won't be long before something similar to Web Clip appears in Microsoft's operating system.

What's most disruptive about Web Clip is that the technology undermines what has previously been the prerogative of publishers: deciding what ingredients go into the making of content. With Web Clip, every individual element that appears on a Web page can be viewed on its own, divorced from its original context.

The Greasemonkey extension for Firefox offers a similar capability, the ability to insert user scripts into any Web page to change its behavior. But Web Clip give users control over the appearance of other people's pages without requiring any knowledge of programming. It makes it too easy.

Maybe that's a good thing. Time will tell, I suppose. It will be interesting to see how publishers react when widgets that offer ad-free views of their sites start being distributed.