We can't be 100% certain but it now seems that Marcko's ban from the Diablo 3 beta was on the grounds that he has stated an intention to produce a gold guide which he would intend to sell.
There's a few interesting points to consider.
Firstly there's the point that Marcko, famous for his Just My Two Copper blog and its associated WoW gold guide, was given a Friends and Family invite by a Blizzard employee after he mentioned how much he'd like one on his blog which is called Diablo 3 Gold Guide Blog. Blizzard then discovered (shock! horror!) that he is planning a gold guide and banned him.
Of course it wouldn't be the first time the left hand knoweth not what the right hand is doing at Blizzard but it's certainly very silly on the face of it.
Let's have a look at what this latest message said:
it clear that using the game for commercial purpose, such as for
selling unlicensed game guides, is prohibited. Violating the Terms of
Use can result in a ban, as was the case here."
OK there's a few points that aren't clear. First, is this only a beta restriction? Because Marcko didn't sell anything during the Beta and as far as I know didn't plan to. Or are they planning to prohibit commercial fan sites when the game goes live?
It would be a huge change of direction for Blizzard to suddenly start actively banning players who are involved with commercial enterprises. For there are lots of commercial WoW sites including Curse Gaming, Wowhead, Thottbot, several hundred blogs that are monetised and hundreds of thousands of Youtube videos. If you put something on the internet it's normal for your content to generate money. That's just how Google and Youtube work. This blog is actually non-commercial but I suspect that it will be harder to put out non-commercial blogs in the future as I'm freeloading off Google and I'm sure they'd prefer it if they got paid.
Next, is there something specifically about farming gold as opposed to playing the game in other ways which is commercial? I can kind of see how people might think so because we all instinctively feel that game gold is "money" even though it's not. Virtual game currency is simply a meter, getting richer is like getting higher level. It's an aspect of gameplay and not actually real money. (Although D3 makes this murkier with the prospect that gold can be cashed out). I don't buy the argument that gold is real world dollars any more than killing power is real world dollars - both can be cashed out, converted into money but they aren't money, just the potential to earn it.
So is it wrong to give people tips on playing the game? There's certainly a lot of bitterness towards theorycrafters but it's never before been something the games company has joined in on. Advice on how to level, where to farm gold, what talents to pick all has money-making potential in a game that will be for many people about making real world money. Is it unfair to help people optimise? Immoral even? I don't really think so either.
Is it wrong to sell information in third party transactions? Well it's not an IP violation. There's no copyright in information. If you think about this it's obvious. Ford own the design of their cars but they don't own "knowing how to turn left". Information about a game isn't property of the game company, there's no legal infringement.
It is (apparently) a terms and conditions violation which doesn't surprise me at all. EULAs are one-sided, not negotiated and have grown over the years to give the issuers more and more powers. Legally an online game is basically a private club that can admit anyone it wants.
In the end banning players for making gold guides is hopelessly futile. It's pretty obvious that you can make a gold guide and not connect it with your in-game character name or the real name they have on file for you. In fact there's so much information around you could possibly make a commercial gold guide without even playing the game, just by doing online research. It's possible they could use cease and desist orders but I'm not sure on what legal grounds they could ask for people to not sell guides to their game. There's no copyright in strategies. Trademark violation, maybe. But any legal remedy they use won't stop these guides from mushrooming up again. The internet has proven remarkably resilient to being told to shut up so far.