Kind of important to remember here that just because there was an ELF sign, it doesn't mean ELF did it; not saying this is the case here, but if you wanted to burn down a place for insurance money because you could make more that way than by selling it in current market conditions, it only costs an additional ten bucks on top of the gas for a bedsheet and a can of spray paint, a very sound investment by any measure.
Of course ELF is quite capable of being destructive and stupid enough to have done this, but let's cool our jets a bit until there are some actual facts.