When I started selling miles on flyhub.com my first question to them was how can you ensure I would never get in trouble, and I liked what they had to say about protecting buyers and sellers' identity by acting as the middleman.

That said, this doesn't mean that I'm not taking a chance when I sell on Craigslist for example, but hopefully airlines have better things to do than come after me. And if they ever did, I'll simply countersue.

You do have a point though chasethemiles, some have gotten caught in the past, not sure where and how they were selling their miles, but I'm gonna guess it was not through flyhub.com or sellyourmiles, I researched both companies extensively before selling on their sites.