"Best Seller Lists": a possible rant

Note: This post was actually inspired by a fellow blogger in The New Dork Review of Books, who is a wonderful writer. You can find his post with this particular issue here.

What does being in a bestseller list really mean? From what I know, it basically consists of titles of books that are -- for lack of a better word -- best sellers. In other words, "Which books get purchased the most?" But does being in this list define the quality of a book?

I notice that nowadays, most buyers and some readers do rely on New York Best Seller, National Best Seller, #1 Best Seller, etc for ideas and recommendations. This is totally understandable, as most of the time, the list provides help while in search for a good book. I think we all check out books that are in these lists because they do receive a lot of acclaim -- word of mouth included. It is after all, human nature to want to check out something that is popular, so we can see and judge for ourselves. These lists even become some sort of an aid for buyers to help them with their choice -- to give them options -- which is pretty convenient. This is perfectly fine. I too, choose from it. I even notice that most of the books I read do happen to belong in the list. And who am I anyway, to not read a book because they are there? Pretty ridiculous, if I do that, if I may say so myself.
But I guess my main point here is, I just don't like how there is a common misconception that:

Best Seller = Good Read

I'm not saying though that the books that are included are always bad ones and undeserving. (ahem, like The Lost Symbol by Dan Brown =P) No, not all of them are like that. Definitely not. Most of the time, there's bound to be great picks there. Some titles for example: The Help by Kathryn Stockett, among many others.
I guess all I'm saying is, I always have the urge to burst people's bubble -- and this brings me back to those days when I worked at a bookstore -- when I would hear (some) customers talk like this:

Customer1: *points to the novel* That's a good book.
Customer2: How do you know? Have you read it?
Customer1: No, but it is in the best seller list. It's got to be good.

At times, I know, I can't blame them. But you know what I mean...... right? ;)

I'm probably just rambling on and on with this, and most of the things I said probably are not even valid, but this just irks me sometimes. Maybe it's the 'assumption' that I find that I don't like. But then again, maybe it is just me being oversensitive.
But I'd like to hear your thoughts about this. If I have offended anyone though, I don't mean to do so at all. I am simply stating my opinion. Please feel free to let me know what you think :)