Santa's Blessing refers to an exploit discovered back when RR3 v2.0 was released.  Evidently, there was a slight change in the structure of one of the files that makes up a player's profile, so by moving v2.0 files back to v1.5, the fields were slightly off, causing huge values in R$ and Fame.  If that version of RR3 was then updated to v2.0, the huge values remained.  [There was actually a bit more to it than that, but it's history now, so it doesn't really matter.]  The name Santa's Blessing was coined by an MRR member because this all happened around Christmas.  After a profile has been modified in this manner, it is also referred to as a blessed account.