And then there is copyright! Although lots of people do it, you shouldn't really go around other peoples sites nicking their images. If it was a site I'd made I would be betting the solicitor on the job!
Manufacturers are usually very happy for you to use their images e.g. JT, Dye etc as it is advertisement for them.
However, if a photographer has gone out and shot loads of quality stills for his own site and everyone just nabs them, I would imagine he/she would be a tad pissed!