Update: From a CNN spokesperson:
The photo, which CBS said was taken before the attack, was being used on our air as we reported about the sexual assault. We made a network-wide editorial decision to blur the faces of those around Logan because we didn’t know if those in the photograph were involved in the attack, or not.
Original Post: In an odd decision, CNN decided to blur out the faces of the people behind Lara Logan in the widely disseminated photo taken shortly before her assault in Cairo.
The photo was sent widely by CBS News, and was published without alteration by hundreds of media outlets.
Or as The LA Times‘ Scott Collins writes:
The reason for the choice is unclear. It is possible that CNN worried about legal liability – despite the fact that the image was taken in a public place during a thronged demonstration of pressing international interest and had been distributed through a wire service. By partly obscuring the image, CNN tampered with the journalistic record without explanation, leaving it to viewers to guess whether the network intended to protect or incriminate the figures in the background.
Note that CBS News never said that these people were suspected of committing the crime against Logan. It is possible a CNN producer was simply following a company policy of blurring out some photos, but that was never made clear.