Pyramid Schemes are basically schemes built in a pattern were the sole promoter recruits participants promising a huge return on invested amounts in a short period of time if they in turn recruit others.
The User at the top of the scheme seems to be the one enjoying and in most cases, disappear Into the thin air with peoples investment funds.
Smart Contracts are majorly built on this pyramid schemes where a participant needs to recruit others under his/her up line in order to earn.
This is my reasons why I don't Invest on pyramid schemes or smart contracts and I wouldn't even advice anyone I know to do so.
The Stress Of Recruiting
Personally, I do not have the patience to convince persons into investing on a platform that would require him/her to convince another before they could earn. What if you don't find another who is interested in investing? You end up losing your invested fund.
Pyramid Schemes are Mostly Scams
Majority of the pyramid Schemes that came surfacing ended up running away with investors funds.
No matter how promising they look, I can not be part of it. Come to think of it, how would you invest $100 to get $300 in 24hrs? Where would they get this much money to pay everyone?.
Cons
Smart Contracts are extremely new technologies which could be vulnerable to bugs which could be exploited by scammers.
Pyramid schemes are doomed to fail because their success depends on the ability to recruit more and more investors. Since there are only a limited number of people in a given community, all pyramid schemes will ultimately collapse.
Conclusion
What you see here is basically in my own opinion, yours might differ.
Adon know