As the pool was before, with full statistics, users could check whether their revenue was really ((50/total_shares) * nb_shares). They could also, by talking with each other, evaluate if the pool reported a plausible number of total shares. While there were ways for the pool to cheat, the statistics allowed users to check it didn't cheat too much.
Currently, you don't see realtime stats, but you can compare those numbers on found blocks older than 2 hours, so not such big difference. Also, as I said, this is only temporary solution. Once I'll change some internal things, I'll show realtime stats per actual hour, so everybody will see almost the same numbers as before this last update.
As long as you release data on how much a share is worth, "cheating" becomes possible.
But you can calculate it itself, too. There is no fancy stats now, but I don't hide any needed info. You know how many shares you submitted and how many reward did you get. You also know that one round is worth of 50BTC. There's nothing hidden! You only cannot calculate/use this numbers at realtime.
I was wondering if you had found a way to preserve both openness and fairness.
Yes, described above.
I believe having the value of contributed shares decrease over time would also fix the cheating problem, ensuring that the expected gain of joining is the same at all times.
Tell me how, I'll implement this! But this attitude open completely different way of cheating, I spent on this many hours by thinking. And once I'll need to take a financial risk of pool unlucky/cheating, pool mining won't be for free anymore :-).