There should be a huge amount of prior art for this? Surely before yoga glo there must be ONE video with the same angle?
I'd be interested to know whether arguments used defending against prior art are legally binding afterward. For example if they said "nope, the camera looks to be 1m, not 3ft", would they be unable to consider something at 1m infringement forever?
Yes, it's called estoppel [1] which, amongst other things, basically means, "whatever you say can and will be used against you". This includes whatever comments and arguments they made during prosecution of the patent.