Valve has recently released Portal 2 on Steam for Linux and opened a GitHub entry to gather all the bugs from the community. When one of the Valve developers closed a bug related to Portal 2 recommending that the users disable a security feature, the Linux community reacted.
Before releasing a stable version of a ported game on the Linux platform, Valve usually lets that title in the Beta stages and gathers bug reports from the community, usually on GitHub. This is just the case with Portal 2, and already the bug reports have started to pile up. The Valve developers have their work cut out ahead of them for some time to come.