Heads up! BTCMine has had trouble with VERY LARGE MINERS on the pool paying 0% [greedy bastards without respect]. BTCMine is being forced to move back to a 2% fixed rate. I suggested that he just kick their asses out of the pool since that is clearly a conscious decision to rip off the pool in my opinion [0% makes sense only for perhaps a trial period]. I suspect they will arrive here in due course.
Just fair warning
We already carry the burden of freeloaders, more of them shouldn't matter. As I've stated in the past, BTC Guild won't be imposing a fee unless the costs to run the server(s) are exceeding the income from donations and transaction fees. And before that, I'll probably put up some donation bars to solicit straight donations to the pool. I'm not a charity, but I'm also firmly running this as a side business, not a primary form of income.
Adding a bunch of freeloaders would potentially increase income slightly. Previous users at their current donation rates would be donating roughly the same per day, just split over more blocks. Meanwhile, the freeloaders reduce variance and earn the pool more via transaction fees. At current exchange rates, the extra transaction fees could potentially offset the additional server costs they're imposing on the pool.
Well, I think BTCMine found itself in the position where it was causing a revenue issue. Also, with the new bitcoin client, transaction fees are going to be reduced on average. It seems they are either suggesting 0.005 or 0.0005BTC per 1KB transaction. The new client supports the additional decimal places. I think 0.3.23 is imminent as there are some issues with using bitcoind in it on Windows (32-bit) systems.
Oh, BTW, you found that increased traffic has taken a lot of your time to load balance between bitcoind daemon instances and now you are setting up two additional servers to deal with load issues. That costs you money. If some large free loaders come you way, I don't think the transaction fees will really pay enough to make it worth your time in trouble shooting and expansion which may be solely to the benefit of free loaders [expansion costs money and will easily exceed your transaction fees I think].
It's your pool, and I don't care as long as it works and is of high quality and integrity [which it has been, excusing the current load issues which you are dealing with phenomenally].