Blizzard has announced extensive changes to its recruit-a-friend program for World of Warcraft, with hefty incentives on offer for both recruiter and friend.
Most notable is an exclusive in-game Zhevra mount (a sort of zebra-unicorn thing); players can claim one of these for every friend they recruit who purchases two months of game time.
However, there are also major in-game benefits to both players. Their accounts are linked, and it's made easier for them to adventure with each other.
While adventuring with a character on a linked account, both players will gain triple experience, levelling up three times as fast.
Furthermore, for every two levels the new player earns, he or she can grant a free level-up to a lower-level character played by the veteran. This will be useful if a newly-recruited friend charges ahead of the character you created to play with them, while you're busy playing your max-level main character.
Characters on linked accounts can summon each other once per hour, cutting down on travel times.
Links between accounts only last 90 days, though. Veteran players get 30 free days of game time if their recruit pays one month's subscription.
For more details, check out Blizzard's FAQ.