In reality a class action lawsuit against a games company is more likely to be used to pressure a change of practices or policy, not to personally get those involved any real compensation (apart from the lawyers of course).
R8 has it pretty right I imagine, as Valve's less likely to need it's customers to pressure it in such ways to get it to improve it's practices/policies than certain other companies.
Given the likely risks and values involved, arbitration and retaining the ability to utilise small claims court seem reasonable resolution options at an individual level. The fact that they will reimburse (different to "pay" as being misreported in number of blogs) costs does take an interesting customer centric approach. It's probably not completely selfless of course - they would have worked out it's still a cheaper option than paying / retaining high priced lawyers.
Of course in some jurisdictions (EU so netizens tell me) you can't agree to waive certain statutory rights and the ability to sue. Being lazy, I can be bothered researching to see if the clauses are enforceable in Australia. Of course like most EULA's, until someone actually tests them no one knows how legally enforceable any of the clauses, let alone these new ones, are.
What I find more interesting is the wording of the clauses about the Steam Wallet and Marketplace. Coming after the recent ruling in the EU giving the right to sell 2nd hand software licences, it makes me think that sometime soon we may be able to trade games that have previously been activated on our accounts. If so, it will be interesting to see the implementation and if Valve or the original publisher gets a cut in the case of a Steam wallet (cash) trade - if an option.
Although the scythe isn't pre-eminent among the weapons of war, anyone who has been on the wrong end of, say, a peasants' revolt will know that in skilled hands it is fearsome. -- (Terry Pratchett, Mort)
Playing: Killing Floor - Other Stuff