I don’t agree with Otto. Using absolute URLs is not the best answer.
A lot of people have learned to use a hammer, so when they want to cut down a tree, I guess they naturally reach for a hammer.
I also think the media upload is a very poor piece of code. It seems like this insidious kind of media upload has also infected many other stack, including the hideous media upload in Joomla. So, WordPress is not unique on this point.