I could give you an example of "server load" bringing a server down. A few years ago, there was a coordinated Denial Of Service (DDOS) attack on three corporate servers; they included Yahoo, Amazon, and Microsoft. Ironically it occured on the very same day at the very same time. Yahoo and Amazon was saturated with so many packets they became "unreachable", while Microsoft kept churning away.
While it may not have been the Mafiaboy attack, nonetheless, Microsoft was indeed taken down by a DDoS around the same time period.