How does Blizzard get to notice suspicious activity?

How does Blizzard get to notice suspicious activity? This is where it gets interesting.

Earlier in the wow gold game, before major updates had been released, wow gold farmers with programming knowledge were able to discover exploits allowing them to make a lot of wow gold very quicklyNow, Blizzard employees are able to see the wow gold economy as a whole, and if wow gold prices in the auction house and across the wow gold game as a whole drop dramatically, then it is likely that someone has managed to find some kind of exploit allowing them to make wow gold.

If you buy wow gold from a reliable wow gold seller, you shouldn't get your account banned unless you are buying a really large amountAnything less than 5,000 wow gold is unlikely to attract Blizzard's attention enough to get you banned