Let me paraphrase that right back at you: so, you don't believe in dowsing just because you personally didn't see it happen?
I think we've already established that it's perfectly ok to not believe something in the utter absence of any proof that it happens. If being on several servers and in several guilds I never even heard of someone asked by a GM out of nowhere to confirm that their RL name was, say, John Smith, I think it's safe enough to take the skeptical approach that it didn't happen.
Plus, I think that just as the lack of "Psychic Wins Jackpot" headlines is taken as tentative confirmation of the lack of psychic power, lack of "Blizzard Banned My Accound Because Mom Was Playing On It" (or girlfriend, legally retarded cousin who can't sign a contract for himself, etc) debackles kinda works the same way. There have been even people claiming they've been banned for using a certain kind of keyboard (as opposed to the real reason: macroing unattended) or for being disabled. If Blizzard actually were routinely swinging the ban bat and taken people to court over something like that, I'd expect enough people to jump all over it, because it's something that would make Blizzard sound positively like a, you know:
As for the other objections:
Some were discovered due to account hacks.
In fact this is the only way to get discovered, and which offers Blizzard a good excuse to lock you out without sounding like the picture above. Most of the hacks boiled down to keyloggers, though, so it's not as if it's a threat that hits everyone randomly. Run an anti-virus, activate data execution protection for _everything_ in Windows, and don't install anything off dodgy sites or emails, though, and you're basically as safe as houses.
Others were reported by other players.
Do you actually see a good reason for someone running around telling people "I'm called Jane Doe but opened this account under the name Jack Deer"? I mean, I'm perfectly aware that people routinely do tell friends their RL names and stuff, because, well, we're social animals. But telling them also what data one entered in an arbitrary form they'll never see anyway, especially when it boils down to a confession of breaking the TOS, seems to me like a case of simply too much data. And too little brain.
Others were discovered when the account in question was reported for other behavior issues.
I fail to see why Blizzard would need that information to ban someone for acting like a disruptive a-hole, or why they'd want to turn it from a clear cut case of banning disruptive behaviour into something that would make headlines as "Blizzard Bans Account Because Player's Mother Was Playing On It".
But you are getting close to a real issue, and why that clause is _actually_ there. Just so people wouldn't have the excuse "but there was someone else at the keyboard acting like a jerk while I was on the toilet for 6 hours." It's been a hare-brained excuse ever since MUD times, which is to say, for over 2 decades. Various clauses to the effect of (A) "you are responsible anyway", and (B) "that's a violation in itself, you berk", are there mostly because of that, rather than because someone genuinely plans to get into players' real lives and check that data.
Some were discovered when someone had a billing issue.
... which are pretty much guaranteed not to happen if you use a prepaid card. There is no bank to bounce those, nor an account that could be/get too far in the negatives.
You really should familiarize yourself with the legally binding contract that you agree to every time you patched the game. And your mother really shouldn't be accepting a legally binding contract for an account in the name of someone other than herself. You might also want to familiarize yourself (via the WoW customer service forums) with what sort of repercussions there are for breaking that contract (which you are).
She didn't create the account in my name, I did. I'm letting her play on it. And if Blizzard actually does want to make headline the guys who were that invasive as to ban an account for letting a family member play on it or for even investigating the private data of customers, I'd be most happy to help them sound like the picture above.
But at any rate, all I wrote above is really just fluff. The actual important part is: just like Bigfoot and dowsing, I'll believe that Blizzard actually investigates that kind of stuff when I see some evidence. And in fact, I'm genuinely interested to see such evidence, because I bet I wouldn't be the only one to cancel the account if it turns out they _are_ that invasive of everyone's privacy.