The average player who plays a video game plays for fun. A "twink" as they are referred to play video games to make themselves feel important. What the average player does is really quite simple.
He/She plays an online game and achieves the same goals as every one else. They level up their toon to the maximum level. They join guilds, meet new friends, try to get the best equipment, etc. Then when they tire of it they cancel their account and move on.
What a "twink" does is quite similar except for one key thing. When they get to level 60 instead of continuing to play that character or move on they decide on something quite different. They feel the need to take all that gold they have racked up at level 60 and send it to a brand new level 1 character they just created. That in itself is not too much of a problem. What is the problem is that they take these new level 1 characters and get them to level 19 for example. (PVP Battleground levels in WoW work like so, level 10-19, 20-29, etc) So when they have reached level 19 they cease to continue using that toon other then playing Battlegrounds. That way they avoid getting XP and avoid moving out of that strong lvl 19 position. Level 19 players versus the level 10-16 players almost never pose a threat. But that isn't the problem either. These level 19's feel the need to be more powerful then the players who are experiencing the game for the first time. An average new to the game level 19 may have a handful of gold if he is lucky, while the "twink" can have thousands. That enables them to buy all the best items. But the real problem is the enchantments. Enchanting weapons and armor with massive stats can turn a level 19 twink into an unstoppable player. They can have twice the Hp's as a "real" level 19 and hit twice as hard. That makes the game uncompetitive and makes playing in the battlegrounds pointless for anyone other then the twink.
The company Blizzard has done everything to insure that type of play would not occur. They made level requirements for potions, armor kits, weapons, and virtually every other aspect of the game. But they forgot one. Enchanting. Sadly it is also the one with the most impact.