Skyfire wrote:A pure Zero-Sum DKP system will keep inflation and deflation exactly zero.
The problem with a pure ZSDKP system is that there is no incentive to work on new bosses.
Exactly... it's why many guilds do fine in MC but fail at BWL - because a lot of the bosses take more than just a few tries to learn. My guild had been on Razorgore for about a month of solid tries but couldn't down him because we had trouble getting the same people to come out to every fight. We had said we wouldn't offer bonus dkp for any reason when we first started our ZSDKP system, but once we began to offer some to come and wipe in BWL, it worked out a lot better. Now that we have up through Firemaw on farm, we have stopped giving the bonus dkp except when we down a boss for the first time.
Inflation is unfortunate, but pretty likely to happen unless you have an entire raid group of hardcore raiders completely committed to getting through content regardless of how many wipes it takes. If inflation is carefully controlled, it won't wreck the system; but if it's not, it can easily make dkp essentially valueless.
It's probably a bad idea to give out dkp in a zero sum system for anything besides the items that drop off a boss and if necessary the aforementioned bonus dkp for wiping on new bosses and/or guild first kills of bosses. The closer you can stay to zero-sum, the better.
There are other systems for dkp besides zero-sum that include item bidding and such, but I don't have a real handle on how they work exactly, so I'm not going to try to explain them (though if someone else has had experience with them they should definitely explain it if they can

.)
Keeping dkp fair is probably the toughest thing about raiding as a guild. That's my opinion, at least. The most important thing is that the GM and officers decide together on a system and then stick to it, with any necessary changes being agreed upon by the leadership team before they're implemented.
Sorry I'm so long-winded... comes from being a teacher, I guess.