I agree. Many beginners just invest seeing their friends just earn profits and invest on the same coin and tend to fall into panic sells which in turn leads to loose huge money. So, yes it's our responsibility to alert them of risks involved in it. This would certainly make many think twice before investing. As money is involved its necessary to analyze before investing. This would eradicate many from loosing money.
If you are recommending something, you are responsible to tell also the risk in, not just convincing them that you are getting decent profits and allure them with the potential that they can do the same. A good friend will always concern about the emotion and make sure that whoever they bring to their investment is aware of how the business works.
Though, it's their obligation to do the homework and study things well before starting their investment, it's money and sometimes friends or relatives got some problem when things went wrong about the investment or business.