Farmville Visit by Defendant Results in Mistrial

I heard the story of a defendant in a MN felony trial who, during the course of the trial, was playing "Farmville" on Facebook (I hope I got that right) with 2 jurors.  They discovered it, told their fellow jurors the next morning at court, the bailiff told the judge, and a mistrial was declared.  The defendant claimed he didn't know the contestants on Farmville were jurors, but a search of records determined that he had searched their names.  The defendant was charged with Juror Tampering and eventually pled guilty to the original charge.  The jurors were, perhaps, not "behaving badly" other than reporting it to the whole jury and eliminating any chance of avoiding a mistrial (if there were 2 alternates).  I hesitate to think of the outcome had they failed to report it.