Arms Deal with Saudi Arabia - Really?

Administration Expected To Sell Arms To Saudi Arabia: http://www.npr.org/templates/story/story.php?storyId=130690602

I have a sincere question about this. Why is the U.S. giving these destructive weapons to the home country of the 911 hijackers? Am I missing something? I understand that the idea is to create allies in the middle east, keep our own troops fortified against Iran's weapons build-up, and this deal probably made a great deal of money for the U.S. And it's not like this is a back-door secret arms build-up like what's happened in the past.. I mean, it's out in the open for everyone to see. But is this really a good idea? Someone please enlighten me.

Chloe