We've always considered MMO membership like ponzi scheme--it gorws exponentially, but the number of people interested inveitably reach a cieling--but Blizzard disagrees, and, in the interest of getting you to sign up your friends for PC MMO World of Warcraft, they're offering a free zebra! A zvera mount anyway.
Here's how it works:
For each person you refer who upgrades to a retail version of World of Warcraft and purchases two months of game time, you will be able to give a character on the account you sent the invitation from an exclusive in-game zhevra mount. This unique mount can be claimed through the website, is only available to Recruit-A-Friend participants, and can only be applied to a single character.