The updated Steam Subscriber Agreement (http://store.steampowered.com/subscriber_agreement/ ), as of July 31, 2012, includes a new clause that requires Steam users to waive their right to participate in class-action lawsuits against Steam/Valve, as well as agree to settle all disputes via arbitration.
We as consumers should not have to give up our fundamental legal rights in order to play games, especially those games which we have already purchased prior to the institution of this new clause.
In September 2011, Sony implemented a similar clause in the PSN Terms of Service. However, unlike Valve, Sony saw fit to provide an opt-out for this clause if a user provided written notification to the SNEI legal department.
Steam users should be provided the same opportunity. Do not give up your legal rights.
If you are comfortable doing so, please post your Steam username in the signature comments so that Valve knows its consumers care.