I think you might be ascribing too much to the marketing types. Regardless of the company, a "controlled leak" would probably be someone from PR (credible) talking to a single (or few) outlets. They almost certainly have no idea of (a) what a user-agent string is, (b) that it is logged to servers, and (c) that high-credibility news outlets are monitoring user-agent strings.

I'm putting my money on gaffe.

Considering how obsessed with image, marketing, etc, Apple is, I would be extremely surprised if the Marketing department weren't hugely competent in this matter, including knowing about user-agent strings, logs, etc.

Ask yourself: would Steve Jobs have known about this? Yes, of course. So, why wouldn't the person he hired? This is not a clueless marketing department we're talking about, here... it's probably the most competent marketing departments of any technology company in the world.

Or at this point, they simply don't care, given that:

1. an announcement has been made with a photo hinting at a Retina display

2. it is obvious that Apple is working on iOS 6.0

No one said it was a controlled leak from a marketing department. It could have been managers (at any department, or multiple departments) issuing a statement that the new development software/hardware can be used on the public Internet without worry. I'd imagine the executives or directors would know (or be told) what could happen, and they were comfortable with it.

At that point, it's not a release of information and it's not a leak, but rather a controlled leak.

Occam's razor

Basically what's happened here and elsewhere is Apple's profile is so big now and there is so much money to be made writing and breaking scoops about them that everything is under much more intense scrutiny then before.

Apple is like the country drifter who's been able to avoid the Barney Fifes at the local sheriffs offices but get's caught once the FBI forensic team is brought in.

The expectation I guess is more secrecy. When they're internally testing iOS 7 they sure as hell won't call it iOS 7 before the announcement. They may approach a number of these sites and offer payments for NDA, (this information is presumably more valuable to Apple then it is to Ars so they can just pay Ars). More intentional misdirection.

Meh. It happened before. Apple obviously doesn’t care at all.

in both cases, the products didn't start showing up in logs until after the announcement of the announcement. the cat is out of the bag. there's no doubt at this point that there's going to be a new high-res iPad announced on march 7. it's not so much a controlled leak as it is apple just doesn't care anymore.