Assuming I could craft messages which did not look like spam (to your system), and I could do it really really fast, do you have any throttling options to allow your customer to prevent an excess of mail from adding up too quickly or an alert based on a threshold? (Maybe i'm overthinking it, but I like services that put me in control of how much money i'm spending instead of being at the mercy of botnets)

"Unusual" send activity is pretty easy to spot, especially if it's going to put our customer at risk in any way. We're extremely proactive about making sure that you're aware of anything that might be considered a "surprise" to your service or your wallet.