I use reusable bags all the time when I do my MAJOR grocery shopping. I do not use those flimsy stupid bags that don't stand up! I have the stiff, plastic type that stand up so you can actually bag your stuff without wanting to throw it across the store! Plus they stay upright in my vehicle.
And yes, I hate it when guests hand you their stinky, stained bags. Gross. Wash them once in awhile, would ya?