Gambles have provably fair rules.
Ponzis are scams in which, by design, the author can pull the plug whenever he sees fit.
In the best interest of young people and/or newcomers who might not understand this I would add a new subforum called "HYIP/Ponzi/scams", or directly "Scams".
On the other hand you can never guarantee 100% of the gambling
sites out there are provably fair by any means, not even 10% of
them. Besides they can also refuse withdrawals whenever they see fit.
Even if they could make all their transactions transparent to confirm overall rates of return, and even if they allow all withdrawals, winnings could unfairly diverted to shill accounts they control. Say they have a 99.5% EV and can "prove" that they do on the block chain. That's great! But there's no way for a gambler to know that "real" users don't actually have a 90% EV while shill accounts cart away the extra profits. The only way to tell is to play over a long enough period of time that your own low rates of return diverge with statistical significance from the advertise EV. For a game with large variance, proving such a scam would be costly.
This is a problem in real casinos, but it's much more pronounced with Bitcoin where all you need to make another shill account is a couple of prime numbers.
So I don't really know what Rampion means by "provably fair rules." If he means rules that are understood by all players in advance, things like PonziCoin seem to fit the bill. If he means rules that are provably enforced by the operator fairly against players--there seem to be FAR fewer such services than there are gambling sites.