McDonald's has now said that they are cancelling their FREE smoothie sampling days. They have had such high demand for the smoothies this week, their production cannot keep up with the demand. At least they are telling us this know instead of repeating another KFC fiasco from a while back!
But there is a coupon on their site here for $1.00 off a smoothie or a frappe. I saw an advertisement stating the smoothies cost $2.29 each so this would make them $1.29 after coupon.
Make sure to check your local store to see if they are participating.