Risk of trading CS:GO skins?

I want to buy some skins for cs:go but I'd rather buy them on here since they're cheaper. Is it common that items are hacked/stolen/refunded on CS:GO? Also, does steam care if you trade on Sythe (similar to runescape)?

Thanks in advance, awesome new section. ^_^

 

Common? No. Or you'd see a lot of big sellers getting banned.

I've heard of huge key sellers getting banned. Literally the most popular ones. Some believes a bunch of people reports them out of jealousy. I know one of those traders bought stolen items. By popular I mean high level players with max friend lists that constantly get comments in their profile to buy/sell keys/skins. Of course the news is recent and when it happened to someone a few months ago, he eventually got his trade ban lifted when he appealed.