Before you get too far into this, there is no XP bonus until you get to 3 in a group.

From Wowwiki: http://www.wowwiki.com/Formulas:Mob_XP#Group_Experience

1 person group = 1.0
2 person group = 1.0
3 person group = 1.166 (16.6% bonus)
4 person group = 1.3 (30% bonus)
5 person group = 1.4(40% bonus)

Hope that helps!

Edit:

Wow -

just saw this in my email - maybe this is what you are talking about... http://us.blizzard.com/support/artic...rticleId=20588

Awesome deal!
Our new Recruit-A-Friend program has added features that reward you even more for bringing your friends into Azeroth™. Recruit-A-Friend and earn:
  • An exclusive ZHEVRA in-game mount* when your friend pays for 60 days of subscription time.
  • 30 Days of FREE** WoW gametime when your friend pays for 30 days of subscription time.
Also, from the moment your friend creates a character and starts adventuring with you (including the trial period), both of you will receive these additional in-game benefits:
  • You and your friend will earn triple the experience when grouped together.
  • For every two levels of experience your friend earns, they can grant one level of experience to any one of your characters of lower level.
  • You and your friend will have the ability to summon each other from any point in the world.
For more details on the new Recruit-A-Friend program please click here.
To recruit your friends now click here.