Mark Zuckerberg, Facebook's CEO, is once again courting software developers. Where he once invited them to live on its site, he's now hoping they'll knit Facebook into desktop applications. It's another move to ape Twitter.

Twitter has been an obsession of Zuckerberg's for some time. He tried to buy the message-broadcasting startup last year, but talks fell apart. Now he's set about rebuilding Facebook in Twitter's image. Facebook has announced an "Open Stream API," an interface for application programmers to download the spew of friends' status updates that now greets users when they log into Facebook. In theory, developers will now be able to code a raft of applications whose main purpose is reading Facebook.

Such a raft already exists for Twitter: TweetDeck, Tweetie, HootSuite, and ones with stranger names for users who tire of using Twitter's already dead-simple website. Twitter enthusiasts say they make the service easier to manage, by handling multiple accounts or tracking search terms as they pop up in Twitter messages.

It's a move in the wrong direction for Facebook. Instead of letting third-party developers remix and filter its users' output, it ought to be doing the job itself. In fact, until its latest redesign, Facebook was doing exactly that, points out Wall Street Journal editor Julia Angwin. The News Feed was a carefully pruned version of today's Stream, with only the most interesting items presented to users. Where the Stream is all noise, the News Feed was pure signal. Perhaps some clever developer can reproduce Facebook's lost algorithm in his own application. We'd download that.