I find it ironic that SEO firms are drawing moralistic lines in the sand. As I have stated my controversial opinion here before, SEO is bunk. "White Hat", "Black Hat", whatever, it is bunk.
I've talked a lot about the need for speed. Specifically, the importance of your web pages loading quickly. Images are the number one culprit. Like a vampire, they are seductive and at the same time suck the life out of your site. (By the way, since this article deals with images, I will be using some as examples and this will cause the pages to take a while to load.)