I read it on Mashable.com that Facebook is replacing the “ignore” button with a “Not Now” button. This is a great move from Facebook. It will keep all connections live even if they are not confirmed. This lets Facebook better target ads and searches. It is also helpful for users.
Read here the full article to find out how it works and what it means for you. This maybe the way to go if you are operating a social website with friend request approval.