I lived in Europe for a while, so I've done most of my skiing over there, where the culture doesn't frown upon skiing wherever you feel comfortable. If you wanted to ski a closed trail, you are welcome to, just know that you might not end up at a running lift. If you want to ski through the trees between trails, go for it. Etc.
Here in the US I haven't quite grasped what is accepted. Does the ski patrol simply frown upon things like that (i.e they don't like it but won't punish you for it), or do they take your pass if they catch you? I was about to go down a closed slope at Snowshoe, and some random woman yelled at me. I wasn't sure if that was because that is frowned upon, or if they just had an overprotective mom syndrome. :)