This has been going on for a long time. Time is money. Some people want to have a life AND play the game. For me, the grind from 1-60 was rough - and the grind from 60-70 is the same as 1-60 time wise. Once you have gone from start to the end, grinding to the end gets really repetitive. Let's say you have worked a cetain class from 1-70, and you try a couple of fun classes out, but don't have the time to level them to 70; you still want to have those classes for end-game content [or "Where it's at", as most WoW players call it]. You can pay someone to level you. Some people have more money than time, and they can justify paying those who have more time and skill than money, to level them. I don't have enough money to pay people to level me, and don't have enough time to level myself quickly at all.
The problem with this is, you learn quite a bit of skill during that grind from 1-70, so most people who buy their account from EBay are an absolute joke from a PvP standpoint; they have not learned the mechanics of that class vs. others, and that is what is difficult. On the WoW main site, you can go to a forum for your exact server, and trash-talk each other. A very common insult for someone who sucks at PvP is to insinuate that they bought their account.
What really sucks is, there was a program that I learned about that gets people banned because a select few abused it. Used properly, it really was helpful. I never got a chance to use it because of the "ban waves" that went on. It is called WoWGlider. It was a bot program that would do all of the AI, and it would grind you automatically; it knew where to go, what to do, would return to town to repair items and empty bags when needed, could even sense when you died so it would run back to resurrect and resume grinding levels. You could set this up and it would do everything for you. The interface was so good that people would use it for "evil" [farming gold, minerals, herbs, fish, cloth, etc.] in such ways as setting it to fish all night and only accept only certain fish or items of value that popped up. People would then sell their bags full of goodies on the auction house for gold, and people were controlling the in-game economy. Blizzard threw it into their terms of service that these third party programs were not to be used, and that they were allowed to temporarily monitor your memory to ensure that you were not using any. Tens of thousands of accounts were banned for this.
There were some people who were praising this program, saying "Thank you - I have 6 Lv 60 characters and an actual social life again from all of the time I do not have to spend grinding!" Unfortunately, I never was able to take advantage of that auto-leveling. It would be sweet to have my characters grinding, one at a time, all week during the 12-14 hours I'm at work, and the 4-7 hours that I'm sleeping.
