I know I will probably get some shit for answering Cro's cooking question last night and now mentioning this, but whatever...
I have all but removed mayo from my diet now. One of the 2 hold overs was tuna salad since it just needs something to make it creamier. Greek yogurt is a perfect replacement. If anyone else likes tuna salad but doesn't want to eat or keep mayo around, non-fat Greek yogurt works great.
I know wren is going to run right out and buy some Greek yogurt since he knows mayo is awful.