What should you do? Well the first thing you should do is NOT to buy them or sell them on eBay. Sale of recalled items on eBay can get you into hot water so if you have any listed you need to end them now.
If you have purchased any Shrek glasses, due to the risk of toxic cadmium in the decorative paint according to the Consumer Product Safety Commission, you should return it. If you purchased it on eBay do not return it to the seller, instead you cna take it to any local McDonalds for a $3.00 refund.
According to a story from UPI (http://www.upi.com/Odd_News/2010/06/09/McDonalds-offers-3-for-recalled-glasses/UPI-78511276111846/ ) you will need to take the item inside the store (you can not return it via the drive thru window).
A manager will have you sign a return receipt and will give you $3.00 per glass.
See the McDonald's website ( http://www.aboutmcdonalds.com/mcd/our_company/mcd_faq/shrek_glasses_recall.html) for full details on the voluntary recall of the glasses.