well lets say you have $5.
Company A says, if you give them $5 dollars now, they'll give you a piece of paper tied to the value of the company...currently worth $5, if the company is doing well, that piece of paper could be worth $8.
The reason people freak out is, if that company says, 'that piece of paper is going to be worth $4' instead, why would you give them $5 for something you could get for $4 later. Instead you can take that $5 and give it to someone else who's going to make their piece of paper worth more, and then with the money you've made, get that old piece of paper for $4, and let it go up in value to $5.
Hope that makes a bit of sense.