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One XPRT's lawyers was quoted by Reuters accusing eBay of "trade secret theft, along with sheer patent infringement." The plaintiffs claim that they shared their ideas with eBay in confidence years ago, so the big company knew they had invented certain e-commerce technologies when it starting using the technology in 2002 and applied for patents in 2003. By applying for the patents, it supposedly acknowledged that the intellectual property was of value.
The XPRT patents connected to the lawsuit include U.S. patents 7483856, 7567937, 7627528, 7610244, 7599881 and 7512563. You can read the whole saga in the formal complaint, which is available in a massive PDF file.