The danger of throwing around ideas is that they get easily stolen by others, turned into reality and passed around as if it was their idea. Since this is the internet, putting out your ideas will give others ideas about it and not everyone is honorable to include you.
This is not a reality though. Ideas are worth nothing. The execution of an idea is the only thing that matters. Let's take for example, Bitcoin. People have had the idea for decentralized currency for decades, the issue was that nobody knew how to do it in a way that guaranteed security and accuracy. There are millions of ideas in the world that simply haven't been executed well. Flying cars, purely P2P exchanges, generalized AI, etc. These are all great ideas that mean absolutely nothing because nobody has been able to implement them in a meaningful way. So, I think sharing ideas is actually good for society. Most people don't have the capacity to execute an idea well, so giving someone else the seed for thought who might have the ability will only benefit the rest of the world.