I am glad this topic has come up. I personally am not a MB owner, but I joined this site in hopes of doing some research on MB fires. My father's 1999 ML320 with 50k on it went up in flames in a parking lot a few weeks ago.
My step-mother drove it and nothing was wrong. She parked it and went into a store to do some shopping. After only 5 minutes in the store, there was an announcement that a silver ML was on fire. She went outside and saw the ML engulfed. Within 7 minutes it was completely gutted. According to the fire dept, a short under the dash started the fire. This was a completely stock ML with no electrical mods done to it. The fire was contained to the interior only. Unfortunetly, my father lacks the time to go through a big legal battle with MB. Instead, my father's insurance gave him blue book and the ML is gone. We don't even know if MB even investigated the fire. The last I knew, the insurance company had it towed to their own lot. According to the insurance co, they will not investigate and press charges against MB as it costs more money then just writing it off as a loss.
In the end, MB gets away with this and doesn't have to pay a dime for what was most likely their fault.