Don’t give bullshit advice. Don’t tell an entrepreneur whether you think his idea will work. You don’t know. You have absolutely no idea. Entrepreneurs have to see around several corners. They have visions for a future that doesn’t currently exist. That vision currently doesn’t exist because the product hasn’t been made in just the right form and/or because the world is just not ready for it. Yet. And you can’t predict how or when the world will change. You may have decent product intuition, but the great achievements in innovation are so massive precisely because everyone else got it wrong at the time. Don’t be that guy.
This doesn’t just apply to entrepreneurs. Most big company types could use this dose of reality. Just because you’re big, it doesn’t mean you can predict the future. This is why most startup acquisitions fail. The hubris of leaders in established companies overwhelms the vision of entrepreneurs.
Very rarely do ideas in big companies fail because they’re bad ideas. They fail because of bad execution.