Can we balance PvP theft success rates based on some social good to make it 1) true and 2) reasonably obvious that, on average, thieves are a good thing for Thera's typical adventurer? Where OOC all reasonable players might say, "Yeah, you got stolen from, but you'd be even worse off without thieves around anyhow, so quit whining" -- ?

Heh, the following constructive example was far more complicated to lay out than I expected (imagine that!), but I think it can be simplified or expanded to taste, and so I provide suggestions along those lines. Regardless, this is really just meant to start a discussion, so I'd rather hear your suggestions. My own opinion is rather abstract: that the ability of a thief to steal from other players should be significantly influenced by their "success" in acquiring goods for other players, voluntarily or involuntarily. (Not to turn players of thieves into Altruists of the Year or anything, but just to someday hear general agreement when someone suggests, "Play a pickpocket, the game could really use one right now.")

Swag Familiarity

Anytime a thief steals an item from a mob (using the actual "steal" skill, not simply looting a corpse), there could be a chance (maybe 100%, but maybe less) to improve a thief's swag familiarity. This variable in turn could influence the thief's success rate when stealing in general, for better (if high for the thief's level) or worse (if low for the thief's level). Swag familiarity could be measured in terms of monetary value, so the value of the item stolen would determine how much swag familiarity would improve or decline. (For the sake of simplicity, I wouldn't consider stolen coins as items for the purposes of swag familiarity. All other items seem easier to account for, though you might also discount consumable items, especially things like scrolls that might crumble on their own). Swag familiarity could be secretly measured without influencing steal success for some time to help determine what is typical for a thief of each level and where unintended consequences might arise.

I expect this system would need the following checks/balances to ensure that swag familiarity only benefits thieves based on what they contribute to the real mud economy (not what they consume, give to NPCs, or spuriously transact).

1) There should be a proportional chance to lose the full weight of an item's swag familiarity whenever it is:
a) given/sold/fenced/bartered to an NPC/mob,
b) sacced,
c) consumed (e.g., eating, quaffing, reciting/crumbling).

Hoarding by logging out is no problem, of course, since you can't steal when logged out. Giving directly to a secondary thief character is no problem since swag familiarity is only gained by stealing from a mob, not stealing or receiving from another PC.

2) There is a likely exploit where a PC gives an expensive item to a low-level mob so that a thief (maybe himself) can easily steal it and get the swag familiarity. The obvious fix is to only grant swag familiarity gains if the item stolen "comes with" the mob when it repops.

3) The final check is really just "implement reasonably." Particularly, make the influential effect of swag familiarity gains/losses gradual enough and powerful enough that thieves are in it for the long haul. Otherwise, one objection to the system might be that thieves will treat swag familiarity as a short-term investment, something to be gained right before a PvP stealing spree and then sold off right after, and that it wouldn't make sense IC to gain and lose talent so quickly through mundane means. To be honest, I think it does make sense that time spent stealing expensive items from monsters would improve skill, and that selling away one's tactile reminders of the experience would worsen skill, such that stealing from mobs could very well make sense IC as a short-term investment in the ability to steal from players. That said, I think the system would be most fun if it also made sense to treat swag familiarity as a long-term investment by engaging in transactions (friendly or unfriendly) with other players and keeping the swag familiarity rather than losing it through consumption or selling the swag to NPCs.

As a final note, Swag Familiarity could alternatively be a hidden stat for all characters as infrastructure for commerce xp or ability to loot in general (so I guess then it would be Loot Familiarity). I focused my example on the "steal" skill to reduce the number of possible exploits, but maybe the long-term benefits of a generic infrastructure are worth working out whatever additional controls might be needed.

Yeah, if you read all that, then you may have forgotten that the above example is just something to start discussion. If we assume "griefing" is inherent to roleplaying a thief in a competitive mud, how might we balance Thief Griefing with Thief RAINBOWS?

I'm evil thief. I don't want to be Santa Claus just so I can continue to rob people.

+1 for the rainbow text, though. :)