It is called a confidence job.  If the first small transaction was never paid ... they would be able to steal one small transaction.  Scammers aren't dumb.  The early payments are in investment in the scam.  Payout a couple early transactions, and now they are "legit".   When the bigger transactions come in they have some "problems".  Interesting that the "solution" to their problems is you sending even more bitcoins no?  Eventually they go silent and just hope to catch noobs who stumble across them without researching first.  When that dries up the site will disappear and a new one with an amazing deal will pop up.

I really am sorry for your loss but once you see a couple hundred scams it becomes very obvious to spot them.  
The brand new site with "back history" appearing out of nowhere - check.
The long time bitcoiner who has never had an account at bitcointalk - check.
The better than anyone else but not too good deal - check.
The big logos of partners which don't stand up (virwox never heard of them) - check.
The swam of single digit users who appear out of nowhere asking about and vouching for the site - check.
The bogus delay tactics and requests for more money - check.


Joe gave you the right answer almost three weeks ago.