Delta just published the Buddy Pass embargo restrictions for 2014.

The GOOD NEWS - nothing is restricted EXCEPT travel to Africa !

Now just use good ole common sense and stay away from high travel Holiday periods.
Such as New Years/Christmas - Presidents Holiday weekend - Spring Break (variable)
Memorial Day weekend - 4th of July (Friday this year-long weekend) - Labor Day weekend
AND THE "BIGGIE" Thanksgiving !#!
These are not restricted but check very carefully - historically these traditional periods are
apt to pose travel problems !