OK To “Use” Someone’s Garbage?

It was garbage day at my place today (and all over Meridian it seemed as I was behind trash trucks on the drive in to work).  As I was rounding the corner of my block, I came upon something I haven't seen before. 

A neighbor seemed to be sneaking yard waste into someone else's trash (he was wheeling it across the street).  I thought this was a bit funny so I turned around and headed back that way to my house.  What I ended up seeing was even more odd.

He was moving from yard waste to yard waste container - house to house - finding room to add his yard waste to what others had already put in theirs.  In a sense, using the extra space.

When I left once again, I was even more surprised.  He had evidently finished the yard waste distribution and was now looking inside the main trash containers to harvest anything he found of interest.

Something struck me as wrong with this.

Now, I'm all for the idea that one man's trash is another man's treasure and I even like the idea of using the entire bin up if you can instead of having to start service, but my suspicion is this is lacking one major factor:  Permission.

He seemed to be sneaking the yard waste in from house to house and I think that's wrong.  If he came to me and asked if he could use my marginal space, I would say absolutely, but to just assume he can or to help himself when I pay for the service rubs me the wrong way.

I also don't love the idea of a neighbor searching through my trash.

Am I weird?  Am I over-reacting?  Should I say something to him?