Starting around 2004, many 3rd party sites popped up offering rake back to poker players (through their website) who were playing at some of the major card rooms. Typically, these webmasters would receive 20-30% of rake that the players generated (under an affiliate agreement with the underlying poker room) and would return a slightly lesser percentage to the poker players thus profiting the difference.
This practice of rake back continued in earnest through 2004 and 2005 and reached a crescendo in 2006 with a seemingly endless number of webmasters offering rake back. Some of these webmasters were quite brash in their advertising, logging into poker sites like Party Poker and posting in the chat box their domain name and their particular offer in an attempt to lure existing players onto their books. In effect, these webmasters were biting the hand that feeds them, robbing the poker rooms of 20-30% of revenue for each player who signed up to their rake back site.
For a while poker sites turned a blind eye to rake back and these rake back websites flourished. The poker rooms were all doing well and the practice was allowed to continue. However, rumors started to circulate in early 2006 that Party Poker, one of the biggest sites on the net, had had enough of the practice of rake back. Empire Poker (and other skins) were the first to suffer, with Party Poker splitting from their skins in 2006 to try to reduce the level of rake back (see this article for more). More recently, Party Poker have started to shut down affiliate accounts that they suspect are rake back accounts rather than legitimate affiliates. Party Poker, however, have realized the value of high turnover customers and have began offering their own internal version of rake back by refunding a proportion of the rake that these high value customers turn over. Party Poker have reduced the middle mans profits by engaging in this practice. One positive from the existence of rake back sites, is that it has encouraged Party Poker to offer such a program.
To date, other sites have not yet followed Party Poker's lead. It is possible to still find webmasters offering rake back for a number of the other larger poker rooms, such as Paradise Poker, Pacific Poker and alike. However, PokerStars have never really offered an affiliate program of note, so rake back has been non existent at this site. This leaves webmasters without the two largest poker rooms to promote their rake back scheme (Party Poker and Poker Stars review). It will be interesting to see how long the practice will keep going.