I'm never sure of the legality of any of this, but, if I can see anybody nearby, I always ask for permission, and, if they say it's nothing to do with them ( usual reply) I tell them where I'll be if anybody wants the item back.
Maybe the main worry for most companies is, yet again, the health and safety aspect. None of them want a claim for injuries received "on their premises" from some skip rat. Perfectly understandable, but I always say I'll mooch about "at my own risk".
When the supermarket war was on, or, maybe just as a result of the recession, teams got sent in to gut places following closure, or, before the new folk could move in.
These guys didn't seem to care a damn, and it's amazing what folk chucked away. Ridiculous, really.
Not always great pickings, however.
I saw a gang move into a Co-op that had been closed. One bloke looked like the boss, so I approached him re a specific item ( old rubbishy plastic pipe, as it happens).
He didn't want to stop working or to speak. Didn't like the look of me, obviously.
Anyway, he went brushing past the first time with head down and a determined look on his face. On his way back, I managed to get my question in. Turned out he was one of those North Walians that can hardly manage the English language.
He still didn't stop, but blurted out in broken English :" Naw, naw, let it be! Keep away! Camera there, look." as he pointed up to an old security camera on the roof.
So I did what I was told.
Two days later, I was back. This day, not only had all the pipes gone off the walls, but somebody had knicked the old camera too!

And to top it all, the old boy's skip was still there and overflowing like an ice-cream cornet! There was as much rubbish around it as in it, and, through it all, I could still see the small piece of pipe that he got so alarmed about.
In conclusion, I suppose I can say:
folk are wasteful and throw thousands of pounds worth of valuable stuff away
and
folk can be very petty about material things, whenever they get the chance to go on a power-crazed ego-trip.
sean rua.