Shopping carts totally gross me out.
And so do high chairs in restaurants.
A while ago (not sure if it was with Sean as an infant or Mackenzie), I picked up a Jolly Jumper Sani-Shopper. Best invention ever. Bought it at Walmart, and do not regret this purchase. I keep it in the car, and love it. This way we always have it handy when in a store or at a restaurant. Whomever invented this - props to you. And, it even covers the handle that I have to push at the store, so I am saved from the dirty cart too! Bonus. Really! (And why yes, Quentin was being lazy while at Costco and was lying down in the top of the cart drinking his bottle.)