If I have an account suspended for botting and have been sending those herbs to a second account Blizzard can consider those accounts linked if the GM bothers to go that far in his investigation and ban/suspend both of them, regardless of what name is on the account. All Blizzard needs is reasonable suspicion. They don't have to "prove" anything.
I think a lot of how far they go depends on the GM, how busy they are, and whether your account has been involved in other issues. I also firmly believe that a 3 day old vanilla account posting 500 auctions a day is going to be investigated a lot harder than a 5 year old fully upgraded level 85 account doing the same thing. Just my opinion and pure conjecture but there you have it.