To be honest, I don't know why it grew to that many. But what you want to do is have referral links from other sites that don't ask their links to be on your site. These are called reciprocal links.
Think of it as being in a neighborhood and of course you want your neighbors to be good ones. That's how Google looks at it, if it thinks you belong to a bad street, it might cause your page ranking to go down. Try to go for vendor listing sites that has a page rank of 3 or higher and where you can put in your link that goes only to your site and not commit to placing their link into your. Do some bookmarking with sites like Delicious and Stumbleupon.
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