Cheap Humble Bundles

More and more people are trading HB for just 2tf2 keys...even less.Some do it for 1tf2 key or a few cards(10-30).

First question..Is it safe buying from them?

Second question...Can one get in trouble for dealing with those guys?

Almost every trader that does this has a lot of rep in a short time span,but not once was he reported.No games or HB pages are disappearing and no one complains.So what's the deal?