What should I do with my Auction rate securities from Merrill Lynch?

I have a Auction rate securities that's actually yielding pretty good money right now. But I got this form in the mail that says that Merrill lynch will buyback my ARS at par value with interest. I have until January of 2010 to take this offer. Why should I give up this great yielding instrument? Since my rate of return is better than anything else out there, shouldn't I at least keep it until 2010? Why are so many people taking up on Merrill Lynch's offer and selling BACK these instruments? It doesn't make sense because the law requires merrill lynch to buy back the full value plus interest as long as the form is submitted before 2010. Why the rush? What am I missing? Great rate, guarantee of return on principal ... Could somebody explain why people are liquidating their securities now?