I think more people should stick up to others when they see a scam on a little kid or a noob people should step up and do the right thing before its too late thats all I want to say
Most scams don't happen where others can see. They either occur in steam chats or in trade. Most of the time the scammer seems somewhat legit (for instance in most quickswitch attempts) so all that other users can do is try to tell new players to be careful when trading, other than that there isn't much people can do to try to stop a scam from happening.
Every group (well any trading/server group) should be anti-scam. It's not just, hey we're dedicated to being against scammers so join us, it's more like, hey we're one of many groups that have a bunch of awesome things but we also hate scammers as well! Many groups have a "report a scammer" section on their steam community page or on their forums. Ex: Mann Co, PPM, TF2-T, Outpost etc.
Hell, I just remembered. The entire front page of SR has a link to a large variety of affiliates which are all against scammers and have means to deal with them.
There are a number of communities that all assist with anti-scamming efforts, whether they be through education, enforcement or prevention. I frequently visit trade servers and always get involved if I see something up, however, it's important to be well informed, you don't want to be the guy who calls everyone a scammer. If you're having issues with finding a safe trading community, I do recommend you check out the sites/servers listed on the SR home page. And if you need further help, feel free to add me and I can try to assist you best I can.