[koromak]

In a website context I think you're wrong, using a scale instead of a crop would result in every image on your page having a different aspect ratio, since the uploaded images probably don't have size constraints.

That would look absolutely whacky. Especially in responsive design, where the aspect ratio of the parent container changes with screen width.

The difference is that thumbnail images aren't TV shows, it doesn't really matter if the image is cut off. Its not supposed to have literal information, its just a contextual hint of what that element is doing / is related to.