Whuffie is the ephemeral, reputation-based currency of Cory Doctorow's sci-fi novel, Down and Out in the Magic Kingdom. This future history book describes a post-scarcity economy: All the necessities (and most of the luxuries) of life are free for the taking. A person's current Whuffie is instantly viewable to anyone, as everybody has a brain-implant giving them an interface with the Net.
A gross Whuffie score looks the same to everyone viewing it, but a weighted Whuffie score is subjective. This meta-Whuffie takes into account right-handed Whuffie (the kind given by people who have received positive Whuffie from you) and left-handed Whuffie (given by people whom you dislike). Another variety is pity Whuffie, given to those who are down on their luck.
A primary difference between Whuffie and money is this: In a cash-based economic system, nobody can gain money without someone else parting with an equal amount of money. In Down and Out
Some people have perceived flaws in Doctorow's conception of Whuffie. For example, it might tend to favor popular speech at the expense of public discourse, and it could be frequently uninformative: if a person has a high Whuffie score, is it for guitar playing or auto repair?
A defender of Whuffie might respond to the first argument by saying that the situation described is already the status quo under the money system, and that the concept of weighted Whuffie helps make better decisions on a person-by-person basis, and thus is more flexible than rating someone by their bank account. A possible response to the second argument is that other information besides a raw score would presumably be available on the Net, such as how a person attained each of the individual points that make up their rating.
Note that Doctorow is not the first to posit such a system. Howard L. Myers wrote of a similar system based on admiration in his story All Around the Universe, written between 1967 and 1971.
Whuffie is mentioned in Doctorow's Eastern Standard Tribe, but appears to be in the general sense of building reputation.
The karma system in Delta Tao's ClanLord MMORPG (originally a Macintosh-only game c. 1999) is a similar system. Both good and bad karma are on record, but both decay with time. Both individual and group vendettas of "bad karma bombing" and organized and unorganized counter campaigns of "good karma bombing" occur. Since karma has relatively little effect on the game mechanics for most players, many players don't care much about it (or at least claim they do not) and both good and bad karma levels for most players stay fairly low.
The online game MapleStory has the concept of "Fame" which was meant to be a whuffie like system, but which has become very close to a second currency. Players can increase or decrease another players fame, ostensibly for helpful or anti-social actions. However, trading of fame for gold or items has become so common that it is now the rule rather than the exception to acquire fame by these means.
The Waddington's board game Careers, released in the 1960s, prefigured this idea of non-monetary motivations. Players could move round the board pursuing various 'careers' and thereby accumulate a combination of 'currencies' they had decided on at the start. The three options were fame (yellow stars), love (red hearts) and, inevitably, money. A star or a heart was worth as much as a dollar.