The OpenDocument Format (ODF) Plugfest gathers together the most important international experts in terms of digital office documents interoperability. At the 2010 edition in Granada I gave the talk below, about the proprietary traps that can be hidden inside ODF documents. The same topic is covered in more depth in this article I wrote in 2007: Hidden traps in OpenDocument (or any other open standard) and how to avoid them.
I also reported in detail what happened at the Plugfest in two separate articles: