does title really matter?

I remember from one of my first classes at the university our professor told us that title of paper is very important. It should tell a possible reader what the work is about. It cannot be totally irrelevant. It's logical, isn't it? I've got used to follow titles and names to understand the essence of any product.
'Rule' about titles works in the US quite well (unless it's some TV-shop thing). This rule used to work perfect in groceries stores back home, but not any longer. Here's the saddest example: I love butter and I buy it quite often. It is much more expensive than margarine and demand for butter is so much greater than for margarine, so some companies started to mix the two and sell it named as 'butter.' Fake butter! That is so frustrating. Unfortunately the rule of reading ingredients doesn't work well here too.