There are a lot of ways to interpret this question

Dangerous in what way?
a. that your money can get lost thru loss in investing?
b. that your money can get lost thru hacking?
c. or that you might get scammed?

there are different types of risks in different types of investments
1. as for example in investing on bitcoin - you can lose your money if you will not be good in decision making on whether you are going to hold on to your coins for larger value or sell it to cut your losses if the price of it goes down.
2. your coins are in danger if you will not be responsible in keeping your private keys on your own. there are a lot of hackers in this cyber world.
3. you are also in danger from scammers who will try to fool you to get your coins from you.

The use and safety of this crypto currency lies on the hands of its users