And if you're a big opera house, try not to turn good publicity into bad.
Putting it another way, Intermezzo has been blogging about opera in London and around Europe for a few years now, and has published many interesting and informative reviews of productions and performances at the Royal Opera House.
Intermezzo got email from the ROH asking her to take down all photos included in her postings that are "referenced to performances at the ROH." In response, she took down all of her ROH postings. She also published the correspondence she received, and her replies. (Do follow that link!)
Look at it this way: the ROH got a lot of good, free publicity from someone who was paying for tickets. Their action has resulted in the loss of that publicity and, I bet, any future publicity.
Way to go, ROH!