Take a thought, leave a thought?

Lately I've been finding a surplus of idea theft, in the form of regurgitation of thought. As an artist, I am constantly influenced and inspired by the works of other people. So my question is: at what point is it considered theft? Is the simple reiteration of an idea considered theft? Some believe that it only gets unethical when there is a strict likeness between a rendering and its original counterpart. How far does this go? Could this be color similarity and sentence structure?

In music, there are entire genres that were created in the same decade or location and it sounds the same. Does this mean that the artists are stealing from each other or does it simply imply that they are being influenced by similar stimuli?

In Philosophy, there are time periods where the same ideas are had by many idealists at the same time. This happens to the point where entire centuries are labeled as The Romantic Era or Enlightenment because many prominent thinkers are all focusing on the same concepts, constantly borrowing and tampering with the last guy's theory. Is this theft? or are we all part of the same experience?

Concepts can be presented and comprehended without even realizing them, but what if an idea is stolen? Once an idea is taken, can there be recompense made? Some things cannot be given back, unlearned, or unwritten. Even when credit is given to an artist or writer who has influenced a piece, it doesn't speak about the time spent developing the idea or the contributions made by everyone involved.

Paranoia is warranted in the world of media, because of the high level of competition. Individuals must be careful to safely present their works so as to prevent theft. A dear friend of mine had an entire premise for a short film stolen by someone he thought to be a friend. Luckily, everyone in Hollywood talks and he caught wind of the theft before the screenplay could be filmed.

The obvious answer could be copyrighting information or ideas so that they cannot be stolen. But there is a loophole in graphic design and other creative mediums. It only takes a change of 10% to circumvent copyright infringement. Fair use hinges on monetary gain from use of an idea, but the usage of an idea can still be labeled as unethical.

Has technology and the onset of 'cut and paste' changed the game and made it more difficult to protect an idea from theft?

Once one removes the focus from the prospect of the negative aspects, there is the question of the benefits of instant access to many ideas and information. Could the ability to access information instantly promote growth within society?