I always think if I saw a shiny quarter in someone's yard I wouldn't touch it, because technically it's on their property, it's theirs. Or it should be presumed to be theirs, just like a lawnmower or a grill on their property should be presumed to be theirs.
I would be very careful about taking anything out of someone's yard. They might see you from the window and come running out with a gun. Or call the police. People do look out the window, too. I did it today, and this is a real coincidence. I went over and glanced out the window and happened to see a guy I know driving by ... at that very second. Let's say I look out the window 5 minutes of the day -- various glances here and there at random throughout the day. If I just happen to look out and see this particular guy drive by, the chances of that are remote.
Anyway, if they looked out it might look like you were sneaking something that belonged to them out of their yard. Which I wouldn't want to happen.
But no one complains -- I've noticed this -- if you clean up after your dog. I've got a bag and it's clearly a bag for cleaning up after my dog. The big complaint they'd have is if you didn't. And again, my presumption is always that someone's looking out their window when I'm walking by.