I feel you should take as much as you want.
It's interesting to see how my thoughts have changed over the last 2 months. At first I was all about offering a community site, taking just enough out to cover hosting, etc. Many people complained I wasn't taking enough commission, that it must be a scam. The only way it could work was if the business model was to run with the investment. It started to feel unfair to me - that I put in all the work and was getting only 1% of the profits. I struggle to decide how much is a fair commission to take.
The more you take, the less investment you will have... the less investment you have... the fewer people that try and work for you for free/share losses/boost max profit.
Another benefit of having lots of investors is that it seems to bring people to the site who would never usually visit a gambling site. They're smart; they're investors, not gamblers. But we've all seen what happens. Investing is slow and boring. Gambling is fast and fun and "I'll only bet a little bit...".
The site will balance itself out in the end, free markets and the like. Right now many people would probably agree the sight has more then enough invested... so maybe taking more then 10% is warranted.
If I ever had a target, it was to be able to offer max bets that compare with SatoshiDice's. At the time they were offering 500 BTC bets at 2x payout. We've achieved that now, and at the same time, their max bet at 2x has more than halved, to 210.6476 BTC at the time of writing. We're still nowhere near their max bet on the "hard to win" end of the spectrum. They offer a max bet of 0.0348 BTC at 64000x. That's a profit to the player of 2227.1652 BTC per roll. It don't see us ever being able to beat that. But I imagine once the new management of SatoshiDice realises what they're offering, they'll realise they can't afford it either and fix it.
You could even automate the process... if you had some set amount you wanted to be invested have a program adjust your take higher and lower each Sunday to try and drive investment to your target without forcing anyone to do anything they did not want to.
Did you notice the effect that the announcement of the commission doubling from 5% to 10% had on the amount invested?
ie. it had approximately zero effect on investment. I guess either
a) investors consider keeping 90% of profits to be pretty much the same as keeping 95% of the profits, and consider both to be a really good deal, or
b) investors didn't notice that the rate changed, so the real reaction to the news is still to come
Either way, it doesn't seem I can manage investment levels by playing with the commission rate, unless I play a lot harder than I have so far.
Also, the 7 day notice period, and a further 7 days until the first commission run actually takes commission at the new rate makes for a pretty sloppy feedback loop.
