Rigging the site to make you lose the free cash doesn't make sense. Most of it will go to the other players, not the site. Take the free $10 and run it up to the 100's and they will make far more than the original $10 in rake. The sites best interest would be to rig it to make every players money last untill it all went into the rake.
A lot of people claim the random number generators are off. But nobody has any real proof. At least I've never seen any published. Since you remember the bad beats you get better than the one you give, memory is just not reliable enough.