Barence writes: "London's Oyster card billing system crashed this morning for the second time in two weeks, forcing Transport for London (TfL) to open gates and allow free travel for all. "There is currently a technical problem with Oyster readers at London Underground stations which is affecting Oyster pay as you go cards only," explains the TfL website. This follows the first crash two weeks ago, which left 65,000 Oyster cards permanently corrupted. Speculation is increasing that the crashes may be related to the hacking of the Oyster card system by Dutch researchers from Radboud University. Plans to publish details of the hack were briefly halted when the makers of the chip used in the system sued the group, although a judge ruled earlier this week that the researchers could go ahead. During the court action, details briefly leaked on website Wikileaks."