What is always annoying about these laws is they simply make criminals out of the honest people and the low lifes don't care anyway. I think back to when i was a kid learning to fish and canoe in the local areas and realize how many times i "broke the law" under this ruling. When your a kid you don't have the know how, information, or will power to go calling people every time you want to do something outdoorsy.
I did some stream fishing in Alaska and found out how bad it is fishing in a over regulated place. Their rule book was the size of a small novel and it was only for the Keni district. We got our butts royally chewed while fishing in legal area because the local landowner didn't want us near his property. We left just to keep the peace.
I also lived in Ohio for a while and found out how tough it is to to do anything when you have no local contacts. Their was a beautiful water fall with some great fishing about a mile from my house but no access. I only fished it once because my landlord knew some old lady well enough that she let us walk a few hundred feet across here property. Most of the locals I talked to knew of it but nobody had been there in years since the access point was posted.
One of my favorite places to fish on a local stream got posted last year. I don't fish there much anymore, but I have several nephews that I am trying to bring up to be outdoors men. It was an easy place to catch catfish, drum, suckers, goldeye, and even an occasional walleye. I saw a lot of kids there over the years. I have no idea who owns the land or even how to find out. I actually thought the land was owned by the town until the signs went up. I can only imagine how tough it would be if that was the case for every place i fished as kid that wasn't directly on a road.
There is local area that is great for hiking. I have taken quite a few young people back there to experience some "non flat North Dakota", and it was pretty great seeing kids that normally would never do something like that having that much fun hiking old cattle trails over the bluffs and stream. Some friends wanted to do the same thing but decided to find the owner of the pasture area just to be sure it was okay. Nice of them right? Well yes, but the owner said he would rather they didn't for liability reasons. I guess he didn't want sued if some dummy fell down a bluff with his permission. I wonder how many landowners would feel the same way?
I grew up teaching myself how to enjoy the outdoors with some friends close to my age. I didn't have a dad who would teach me the ways of the outdoors, and I bet most of my fishing, canoeing, hiking, frog catching, shed hunting, and such involved somebodies unposted land. I can promise you we would have done a lot less if we had to try and find the owners and call them every time. I really hate to see legislation passed that makes it harder for young people to enjoy the outdoors in this day of modern entertainment when they have so many easy alternatives to become the conservationist of tomorrow.