Unauthorized Use of Your Photograph how ethical is it?

Photo Studios using photographs without permission of its customer how ethical is it? yes it is true one of my friend is a wild life photographer more than the hobby it is his passion... recently while chatting with him i saw a status message in his gtalk has "Beware of G.K.Vale" when i asked him he said that he visited to order prints at one of the famous studio Recently and saw his own photographs printed on the broucher without his permission when asked about it staff apologized and said that they will not do the same mistake again and again the same evening when he went to take the prints which he ordered in the morning the manager voluntarily came near him and said that it is their own photographs and they have not used any bodies without permission!!! how can photographer cannot identify his own photos? what the hell with these fraud managers? anyway as it is digital photos which do not have negative it is really hard to prove the copy right infringement any way if you are professional photographer it is better to leave a highly transparent fine watermark which hardly visible to the eye at the bottom of the pictures to avoid and sue these kind of cases!!

so one thing came to my mind is how ethical is to use the photographs taken by others without permission or properly crediting the original photographer and when they get caught claiming that it is their own pictures as in this digital world there will be no hard evidence? the fraudelent was a Studio of B.T.M layout Branch Bangalore..... so guys be careful while giving professional photos to studios if necessary leave a watermark there are so many tools out there which creates a watermark that is barely visible to naked eyes!!!