I had previously been trying to say that ideas are to people as animals are to plants. In this analogy, I would say that ideas are like eggs that hatch in the protection provided by people-plants.
Now I'm thinking a better analogy might be: ideas are to people as plants are to land. In this analogy, I would say that ideas are like seeds that grow in people-land.
One related idea I've been working with is the notion that ideas and memes have the appearance of "hatching" or "growing" inside a person's mind, such that the person has the perception that the idea is "their's", when really the idea was like a seed that probably grew in many people's minds, and was specifically designed to grow just like that in any suitable soil. In this theory, one would argue that the reason people perceive ideas as being their own is really a trick of the idea itself, because ideas that people think are their own idea are more likely to survive and reproduce.
With that said, by the same analogy, the idea that grows or hatches in someone's mind is probably unique, in the sense that a baby born is generally unique from it's brothers and sisters, though they are all likely to be the same species. Also, there is always the chance of mutations, meaning that someone's version of an idea might be different in a way that was unintended by the meme-DNA that was growing in someone's mind.
This idea is also connected to the "copyrights and patents are bad" idea in that it suggests that people don't really own the ideas that they try to patent. I think it applies to copyrights to, meaning that people don't really own the 'art' that they create, though this is more tenuous, since it's generally the artistic artifact itself that is copyrighted, and not the 'idea' underlying the art. Still, I think copyrights hurt humanity by planting seeds in brains that are disallowed from growing in certain ways.