A "report this product" feature was added today to every game on Steam. Simply click on a little flag icon (to the right of where it says "Share" and "Embed") to get the following report window.
There is really no telling what function this will really have as I doubt many titles will be (nor should be) pulled simply for offending a few people, but I suppose we'll have to wait and see. I mean, if offending people or having adult content was all it took to get something pulled, then South Park: The Stick of Truth would not last long at all.
Also the bored trolls that just want to shut something down.
Could you imagine 4chan reporting Half Life 2 enough to get it shut down?
Hopefully it will be monitored first