Once and only once I came across a score of Maple.I cut up all the wood.Then I loaded up all I could and planned to unload and come back for the rest.Got back to my place unloaded and came back and the rest of what I cut was gone.Now I cut and split only what I can carry.Then I come back for more.If someone else has come and cut what was left I'm OK but no more taking my work.
Sounds like good policy to me. No sense in doing another hoarder's work for them. I would add to that grab as much as you can while you're there, because like you pointed out, it may be gone when you go back later.
I live in an area where probably 80% of people are heating with mostly wood. Many of the properties are smaller and don't have their own supply of trees for firewood. We get a lot of dropped trees during windstorms throughout the year and it's become a race to check what's fallen on the roads sometimes. You can drive by a large fallen tree on the road and an hour later you drive by again and it's only a pile of sawdust. Big competition scrounging these days.
If hand loading I only buck what I can haul. I've actually lost wood off private property where I'm the only one with permission. That's really irksome to me. If you need wood that bad, stop & ask, I'll help ya cut & load, but don't steal. We usually deck 12 footers & load with forks, haven't lost any of that.