Marriott is the only hotel loyalty program that allows you to buy back the status that you had the previous year for a set number of points. This Elite Buy Back Promotion has again returned. You can access this offer here (note that you first need to sign to your Marriott Rewards account).
You can buy back the status you had in 2012 through April 1, 2013. The number of points requires is dependent of the status level that you wish to maintain.