Patents are necessary when one person comes up with a great idea and is directly working on it and needs to get ideas from others without worrying that the idea will be stolen. However, when anyone can get a patent and let the idea sit for years without development, then it does hinder growth and innovation.
Patents protect a person's detailed product concept, but sometimes they can hinder others who come up with a similar idea, and really aren't trying to copy the other person. There are even people and companies who own patents just so they can go after people. People who do this are called patent trolls. They generally don't even make the product, so this is a complete disservice, done to earn profit, that limits innovation.
Yes, as a matter of fact, patents have been shown to hinder growth and innovation within society. We've granted so many patents for so many different things now that it's impossible for inventors to publicize anything that might be innovative without spending thousands of dollars on legal fees to find out if someone else already patented a part of what they've done.
There are times where someone has a good idea but is afraid to pursue it because it is thought that there is already a patent pending. And people take out patents at the very beginning of a process and then let them sit for a very long time which prohibits others from getting a shot.
I think that patents can be a good thing, in order to give companies protection while they develop their products, but they also slow down growth and innovation. If someone sees that a company has patented a great idea, they won't try to improve on it on their own way.
The number of conceptual ideas might increase if the patent system were abandoned, but these ideas would wither on the vine without the protection offered by patents. Patents protect investments and without investments the concepts and inventions would never materialize. Innovation and growth would actually suffer because inventors and investors would have no confidence in obtaining returns on their investments.
The patent system protects the investment of capital and thought that a developer puts into his new product. This insures that he will have a fair chance to profit by his product. Without this incentive there would be less new products. If I make a chair and it's sitting on my front porch that doesn't give people the right to take it. It's the same with products of thought.