People are calling in to Blizzard because their service is down. If you think Blizzard wants to spend the extra money to pay their CSR's just to catch botters, you're not very bright. That's not how business works.
Blizzard doesn't intentionally bring services down to catch anyone. The more their services are down, the more time and resources they have to put into fixing and supporting issues. It's a lose-lose situation when their services are down.
And that GM you talked to, SkuaR, was an idiot. Not only can they add the RAF to the email, they can actually create starter accounts on the email as well.
It's been said time and time again...You really have to mess up to get blizzard to research all the accounts under a single b.net account. In almost all cases, it's not worth the extra effort to ban all the offending accounts, they ban the one they find and move on.
And probably 99% of all multi-boxers are legit players. By no means does blizzard instantly assume you're a botter if you have multiple accounts under a single b.net account.