No… you shouldn’t regret since you said you already advised everyone you invited. But you see, Ponzi scheme is like a spirit for greediness and if one isn’t careful, they could be scammed in a huge way. I can’t count numerous Ponzi schemes I have entered years back. Get rich quick scheme is never a good thing. One would regret later on because there’s no way greed won’t come into play. But you did the right thing to inform them on time of the risk in there.