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When Bing debuted a feature called Cashback, the product was intended to save users money while they shopped from online retailers.

As we told you last month when discussing the program's early successes, Cashback works by giving users a certain amount of money back every time they search for an item and then buy it from a participating store. But some users have found the opposite to be true: Retailer cookies trigger jacked-up prices for some items, causing a phenomenon one man calls "negative cashback." How much do Bing users stand to lose? Read on, and brace yourselves.

The Inside Source is eBay's latest announcement. The searching, buying, and selling habits of its 88 million active users have added up to an enormous dataset, one that could have easily been hoarded and sold to marketers, brands, and others with a vested interest in online retail and trends.

Although eBay isn't releasing raw stats into the wild, it is publishing editorial content and news on trends as well as a tag cloud of most popular searches right now. Coming soon are multimedia galleries and real-time visualizations of current eBay searches. Can we get an open API? Read on to find out.

Online retailer Amazon.com has just announced a new checkout system called "PayPhrase" which speeds up the process of making online purchases by allowing shoppers to enter a unique phrase and 4-digit PIN number to complete their transaction. Both the phrase and PIN are created in advance and are linked to a shipping address and preferred method of payment. After the initial set up, PayPhrase users are no longer required to sign in or fill out credit card information when shopping online.

Social networking sites are quickly becoming one of the most important places where retailers can meet potential customers and interact with their current customer base. According to a new report from eMarketer, social network users are a lucrative target demographic because they are more likely to make online purchases than any other group. About three-quarters of all the retailers in the Internet Retailer Top 500 Guide maintain a presence on at least one social network. Facebook, YouTube and MySpace are the most popular social networking sites for online retailers.