David,
If someone asks permission then fine.
What happens if one of your direct competitors steals your images and gains an advantage over you?
Anyone using someone else's collateral (images etc) should ask permission first, including mine!
I can't police the whole internet, and life's too short anyway. I should watermark my photos. Most of us have lots of usable information (to the competition) on our websites. A little give and take is OK by me.