I suspect we're talking almost negligible numbers here too as far as miners are concerned.

If , hypothetically, the fee was 0.3%, this represents;
1)  A not insignificant income to WK (As this stands at the mo approx 6TH of gross income)
2)  An insignificant impact on miners revenue

There could potentially be a tiered fee system too (To account for the effort required to fix a problem if a miner is sending 1gh or 100th, are pretty much the same.  So a lower fee %  the more hash rate you are sending to the pool, based on an average period or whatever).

I don't have a problem someone being rewarded for their hard work, and providing a valuable (profitable) service..