it looks like her chair decided to give up the ghost. maybe she is too fat for the office chair to support her weight, either that or some funny bastard pulled on that little lever without her knowledge.
They are, and indeed this began with local news before they did it nationally (at the BBC), but they still have manual locking mechanisms on the camera bases and tripods.
Blue screen behind presenter, scene is computer generated, so no matter where camera points within blue screen the image remains fixed.
No, the background is back projected in most cases. If you were in the studio you would normally see a blue or green background. In effect, the camera on the presenter is placed in front of an electronically or computer generated 'back' projection (which the news reader doesn't see of course). This is the same with the weather forecasts. Usually they use a permanently mounted camera outside the building and simply 'mix' that in. For example, BBC Lincolnshire have a couple of cameras aimed up at the cathedral from different strategic points. Anyway, that's why it didn't move and also suggested it was the camera that moved. The camera is (as OLM noted) operated by a computer (though to an extent as there is usually a tech op or producer/director as well), so that was either a faulty command - and a rather strange one, or as I said earlier the camera cradle on the dolly/tripod wasn't locked off. EDIT: I hadn't seen Fullback's response before posting!
Still doesn't seem logical to me, but hay ho. I guess the bigger clue it wasn't the chair was the lack of reaction from the presenter.