The New York Times had an interesting story today about people who gleaned from the gardens in homes that were abandoned and/or foreclosed upon. Apparently, it's illegal to pick the ripe vegetables in the gardens and fruit on the trees in the yards of abandoned homes. However, no one seems to have had any problems doing it yet. With the number of foreclosed and abandoned homes rising, this may become more commonplace.
Granted, I can see how it would put off a real estate agent and potential buyers to see someone foraging in the garden, but if the garden itself is overgrown and neglected, I'd say the house and the yard isn't faring much better. These are abandoned and foreclosed homes--not homes where the owners just went away for a couple of weeks.
Now, I have two garden plots--one that I split with the organizer of a community garden in my town (a project with the Council on Aging and the Youth Commission), and one at work. There are "No Trespassing" signs on the plots at the community garden at work; apparently in one of the locations, some people have been picking the produce. My position is--if you are willing to help me gather and lay down some seaweed mulch, weed, and/or help out with putting up a chicken wire fence around the existing fence, I'm happy to give you some of my produce (if it comes out okay--my tomatoes there are falling prey to blossom end rot).
If I had a garden that I had to abandon for whatever reason, it would break my heart to think that the produce would go uneaten, and unenjoyed. I don't have a problem with people gleaning crops that would otherwise rot on the vine (or the tree); I have a bigger problem with that delicious food going to waste.