FWIW here in Portland, OR, a trailer attached to one's bike outside the grocery store would be at risk of being stolen. That's a key reason I bought a Travoy, as it's easy to detach and take into the store to shop. We have a large homeless population, and many of them use anything with wheels to haul stuff (trailers, baby strollers, shopping carts). Same goes for anything on a bike that's easily removeable. I've had to replace two different tail lights that I'd forgotten to take into the store with me and were gone when I came out.
Another reason I got the Travoy is to be able to haul cases of mineral water or wine, as well as large bags of dog food. Seemed silly to pop into the car and drive less than a mile to pick up those things. That was my rationale/excuse anyway! And with my REI member dividend it was almost 'free' :-)