Most discussion on this topic needs examples to be meaningful.
Damn near all design comes from precedents, not much is 100% invention …
So what is wrong? In copyright law, it is ‘derivative work’ where… the prior art was needed to achieve the derived work. A tracing is an example. If you need a silhouette of a horse (or a unicorn) and you trace a photo, even if you bend and alter it, you have created a derivative work and owe the source some credit, and require permission.
In patent law, it is using someone else’s innovative process or method, while it is still protected. You can ethically accomplish the same THING that they accomplish, by your own route, your own methods, and be totally clear. That encourages others to come up with more efficient methods, innovative methods. So, you cannot patent the idea “a can that cools the drink inside it without any external power source” but you can patent one particular way of doing this, if it is innovative and original.
Low-level copying is cheap and unimpressive, maybe even dishonorable, but … it is going to happen. You can’t protect everything, nor should you try to.
I think that the law has evolved for the most part along the lines that society needs… to protect things that should be protected, to give innovators proper incentive to develop new things and exploit them. Limits on copyrights and patents are good, if they require the inventor to quickly bring to market their innovations for the use of the society, and still provide for them some tiem to profit from their innovation.
The way you first asked this question though, very broadly, it is in the gray area…
I do think that novelty for novelty’s sake is a contemporary fetish. Folks should relax a bit and realize that their totally innovative sports shoe, is in fact still a shoe which shares 95% of its design DNA with things that came before, if not more. Likewise, the shoe that is more innovative… is less likely to be a good shoe. You are a designer, not some creative deity making life from clay.
I get turned off by people that say that everything that can be designed, has been designed… an old boss of mine said that and I lost respect for him.
But, everything you design… comes from someplace. Nothing wrong with that. Cut and paste HTML code? That is lame. Learn how to make CSS so that your columns work nicely? That is just learning. Logo with a wolf head? Depends. Logo with a big swoosh? Lame, probably, once 10,000 other swooshes are out there. Criminal? Not hardly.
This whole cheat/copied/zeroscore/theft/plagiarized thing is usually pretty easy to see, when its right in front of you and the context and evidence are at hand.