proposed a protocol to exchange reputation data. It was originally aimed at email applications, but it was subsequently developed as a general architecture for a reputation-based service, followed by an email-specific part. However, the workhorse of email reputation remains with DNSxL's, which do not follow that protocol. Those specification don't say how to collect feedback —in fact, the granularity of email sending entities makes it impractical to collect feedback directly from recipients— but are only concerned with reputation query/response methods. Notable examples of practical applications Search: web (see PageRank) eCommerce: eBay, Epinions, Bizrate, Trustpilot Social news: Reddit, Digg, Imgur Programming communities: Advogato, freelance marketplaces, Stack Overflow Wikis: Increase contribution quantity and quality Internet Security: TrustedSource Question-and-Answer sites: Quora, Yahoo! Answers, Gutefrage.net, Stack Exchange Email: DNSBL and DNSWL provide global reputation about email senders Personal Reputation: CouchSurfing (for travelers), Non Governmental organizations (NGOs): GreatNonProfits.org, GlobalGiving Professional reputation of translators and translation outsourcers: BlueBoard at ProZ.com All purpose reputation system: Yelp, Inc. Academia: general bibliometric measures, e.g. the h-index of a researcher. Reputation as a resource High reputation capital often confers benefits upon the holder. For example, a wide range of studies have found a positive correlation between seller rating and asking price on eBay, indicating that high reputation can help users obtain more money for their items. High product reviews on online marketplaces can also help drive higher sales volumes. Abstract reputation can be used as a kind of resource, to be traded away for short-term gains or built up by investing effort. For example, a company with a good reputation may sell lower-quality products for higher profit until their reputation falls, or they may sell higher-quality products to increase their reputation. Some reputation systems go further, making it explicitly possible to spend reputation within the system to derive a benefit. For example, on the Stack Overflow community, reputation points can be spent on question "bounties" to incentivize other users to answer the question. Even without an explicit spending mechanism in place, reputation systems often make it easier for users to spend their reputation without harming it excessively. For example, a ridesharing company driver with a high ride acceptance score (a metric often used for driver reputation) may opt to be more selective about his or her clientele, decreasing the driver's acceptance score but improving his or her driving experience. With the explicit feedback provided by the service, drivers can carefully