Ah, I think tagging, watermarking or only displaying it in very low res etc largely just makes the photographer feel special and lifts their ego, like their photo might be so good that someone will use it to make lots of money or something...yeh right
Anyone, or a company, actually with the sort of money to make it worthwhile wouldn't steal the thing in the first place in my opinion and would ask first.
Just my thoughts on it....perhaps Apple or Microsoft will steal one of my images one day...then I could have some fun
Mike