I only have about 0.1 BTC to go before I break even.  So I'm at least not on the hook for a significant amount, and I have sworn off buying more contracts.  However this thread definitely did help to open my eyes about bitcoin mining schemes in general, and contribute to making me more cautious and skeptical.  The idea of paying a lump sum for a cloud mining contract, with the eventual outcome that you perhaps (hopefully) earn back the same amount of BTC, makes it similar to a mail in rebate.  You pay money up front for an item and the promotional gimmick from the company that made the product is that they will mail you a portion of the money you paid up front at a later time.  During that interval of time they can earn interest on that money.

http://en.wikipedia.org/wiki/Rebate_(marketing)