Did this guy really get banned?

The thing to keep in mind in these situations is that there are two sides to every story, and no one but our Game Masters are able to see both sides of the situation. It's very easy for someone to tell you they did nothing wrong, and while that could be true, there are likely other contributors that factor into a suspension or ban. Simply transferring gold may not be the only outlier in this situation.

As I have not conducted the investigation into the account, I'm afraid I cannot say what the circumstances were. And unfortunately, even if I had been, I would not be at liberty to do so, as that is between the player who received the suspension and our Account Administration department.

If you are in a situation where you feel your account was incorrectly suspended or banned, you are always welcome to contest it via e-mail at wowaccountadmin@blizzard.com, and I recommend your friend do so if he wishes to regain access to his account. It's best to contest these things sooner rather than later, as the longer you wait, the fewer logs we are able to utilize in these investigations or overturns.

In short, to answer your question: Could it? Yes. Does it frequently? Not so much. Those who post similar stories on the forums have something in common - they wish to contest it and the forums are the first place they think of going. This does not mean it happens to a great number of people.