...Since it's trustless the only thing you can compete on is fee, and so it's a race to the bottom. The fee would have to end up at zero.
See also: dice sites, exchanges, and anything else currently taking a fee for a service that can be decentralised and made trust-less.

Hi doog, much respect to you for making just-dice and all the work you do on this forum regarding scammers etc.
I just wanted to chime in and say fee is not the only thing provably fair ponzis can compete on. It can be the mechanisms themselves. For example how often payout? How much. Will there be levels for each investor, can you pay more for a bigger return etc.. There are many things to compete on, the idea is to make it fun and rewarding, and this is just the beginning.
Giving this a thought, you are right, the fee is not the only factor. Time may be perceived as one factor, but is it so influential? What difference does it make if payments are made every hour or every 10 minutes? If they are made too often, the scheme would get stuck due to lack of funds, and this would discourage new investors. Regarding time, there might be a prompter-like attitude with gradable profit factor- if the scheme is in need of new funds

then instead of 150% you will receibe 300% but this would mean that the scheme would go further and deeper into debt, as Dooglus nicely called it an increase in liabilities.
I've spent some time today reading about Ethereum, as a solution (also) suggested by Dooglus, I went through their whitepaper and in terms of security, from the perspective of the people who risk their money, it really seems a good idea to run such a Ponzi operation with the use of their service. It becomes trustless, the only minus being the cost of Ether- of sustaining the operation with the native currency, but I guess it would be comparable to the managment fee/system maintenance. Thus, a good suggestion by Dooglus.