Do different speaker cables and interconnects make a difference?

I am so getting flame for this. If you disagree, and I am sure there are millions of you out there and going to leave a comment, at least please make it intelligent instead of the usual 'snake oil' , 'you idiot' comments.
I do however believe that the mark up on speaker cables are ridiculous and it's the most over priced item in the stereo world. I am not saying I agree with it and I am one who will never pay retail price for cables. I am however saying that cables do make a difference. The question of price is a question on speaker cable value and it's a completely different debate.