Small problems, but made large due to the nature of the game.
It's been a bit of a rough week for Blizzard on the Diablo 3 front. There were not one, but two bugs that let players breeze through even the hardest difficulties with ease; the first was a glitch that could make a wizard completely invincible, and the second was barbarian exploit that made the game think that the skill furious charge was always on when moving into enemies, when coupled with the proper rune this provided pretty much infinite regeneration.
Although the bugs have since been fixed, there were multiple instances of people using the glitches, especially the wizard one, to farm inferno with ease. Normally in a game like this it would be a pain, given that people shouldn't be able to get some of those available items without some serious time and effort, but it wouldn't be a huge deal because there's always going to be more items. However, due to the way Diablo 3 works in particular this culminated in a much larger problem.
The first problem is one that was also present in Diablo 2 as well, but not as pervasive: it's the idea that online you're going to run into a lot of ill-gotten loot. This was a major problem in the previous game, with cloning and hacking running rampant. The thing is though that you could play offline if you wanted to avoid all of that stuff, but this time out it isn't really an option. That seems like a rather minor complaint I'll grant you, but it also plays into the next, rather major one: people probably made a decent amount of real world money off these exploits while they first existed.
Since the auction house in D3 was one of the first to take real world money, who's to exactly say who might have been using this exploit while it was still relatively unknown in order to easily fatten their own coffers? Blizzard might be able to trace some of the stuff back, but there will be people who get away scot-free mostly because there's just so many people out there in the player base.
This is sort of an early lesson, because as more games adopt these kinds of systems, there's more potential for some actual damaging stuff that looks kind of like this to happen. I'm not saying that it was a disaster or anything, but it was something that people were definitely paying attention to. The bugs didn't remain in the game for too long, but let's face it, they got out there for long enough that there could have been a slew of problems coming out of this.
As games become more integrated, people are going to have to be ever more vigilant. I guess that this was just an early lesson in that cause. Probably won't be the last one either.