Some interesting things have been found in the game files - error messages that appear to relate to in-game abilities based on the recruit-a-friend facility.

Currently, if you invite a friend to World Of Warcraft, you receive a free month's subscription fee, and that's it. The error messages that have been discovered make it look like there will be the ability to "Grant Levels" to your friend, and maybe "Summon" them. Here's all we know so far:

• ERR_REFER_A_FRIEND_SUMMON_COOLDOWN = "You can only summon your friend once per hour.";
• ERR_REFER_A_FRIEND_SUMMON_LEVEL_MAX_I = "You cannot summon players above level %d.";
• ERR_REFER_A_FRIEND_TARGET_TOO_HIGH = "That player's level is too high.";
• ERR_REFER_A_FRIEND_TOO_FAR = "That player is too far away.";
• FACTION_STANDING_INCREASED_BONUS = "Reputation with %s increased by %d. (+%.1f Refer-A-Friend bonus)";
• ERR_REFER_A_FRIEND_DIFFERENT_FACTION = "You cannot grant levels to a character of the opposite faction.";
• ERR_REFER_A_FRIEND_GRANT_LEVEL_MAX_I = "You cannot grant levels to players level %d or higher.";
• ERR_REFER_A_FRIEND_INSUFFICIENT_GRANTABLE_LEVELS = "You have not earned enough levels to grant any more levels.";
• ERR_REFER_A_FRIEND_NOT_NOW = "You cannot grant that player a level right now.";
• ERR_REFER_A_FRIEND_NOT_REFERRED_BY = "You were not referred by that player.";

Obviously, Blizzard may never implement this.