This is a particularly good story on private "speech codes" maintained by Internet companies and the impact they have on people's discourse.

Companies in charge of seemingly public spaces online wipe out content that's controversial but otherwise legal.

Dutch photographer Maarten Dors met the limits of free speech at Yahoo Inc.'s photo-sharing service, Flickr, when he posted an image of an early-adolescent boy with disheveled hair and a ragged T-shirt, staring blankly with a lit cigarette in his mouth.

Without prior notice, Yahoo deleted the photo on grounds it violated an unwritten ban on depicting children smoking. Dors eventually convinced a Yahoo manager that — far from promoting smoking — the photo had value as a statement on poverty and street life in Romania. Yet another employee deleted it again a few months later.