Clint Watson put the question to artists about buying photos to use for paintings.   Photos, like other research information, can give the painter greater understanding of a subject he, or she, is unable to view in person.  Animals, children, people in action can't sit still for a painting.  Try to get a sunrise or sunset to "hold that pose".  Nothing gives us insight more than being there.  However, we can't be everywhere to see, feel, hear, touch all things.  What we can do is paint as often as possible from life to gain knowledge of shapes, light, shadow, etc..  Then apply that knowledge when we need to use the information found in a photo.  Richard Schmid has spoken of this several times when, after having painted a subject many times in similar lighting, he could use a reference photo to duplicate the experience.  The resulting artwork gives the viewer the sense of having been there.  The problem I find with photos is they want to be the boss.  The painter can get caught up in trying to put everything in the painting they see in the photo.  The photo screams for duplication!  So the question I must ask myself is what is my reason for painting? Is it to recreate a photo or to create a beautiful painting?  Sharing photographic information, like sharing technique or material information, is another way for painters to grow.  I say bless those who are willing to get the information out there.