Blizzard’s offering free mounts and experience for players who recruit their friends into World of Warcraft, as you can see on the official site.
Get someone involved and get them past the first two months of paid game time and you get your exclusive steed. From the site:
How can I earn the exclusive in-game mount?
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.
What in-game benefits do we get while the accounts we play are linked?
1. Characters on both accounts can summon each other once per hour.
2. While adventuring with your linked friend/family member, you will each gain triple experience.
3. For every two levels the new player earns, the new player can grant one free level-up to a lower-level character played by the veteran player.
The rest’s through the link.