oil candle spill/residue?
I had wondered that too; more plausible than leaky lawn mowers and edgers IMO.
Not very likely; actually, not likely at all, from what I saw of the damage firsthand this morning. I arrived shortly after 9:30am (street parking opens up then) and walked the entire length of The Wall, from east to west, with video camera rolling. The oily-looking dribbles began at Panel 48E and continued all the way to the west panels. I don't have the exact panel numbers that were sprayed, because I am just now watching the video. I will post more info as soon as I have gone through the video.
And I will post the video on You Tube, hopefully before nightfall.
It also appears that the same oily stuff was dribbled on the pedestal for the nurses' (at the fallen soldier's feet) statue and the walkway around it, though not as extensive as The Wall.
There are some similar oily dribbles at the cobblestone by the Brothers statue, but the statue itself appeared OK. It is surrounded by a short chain fence and sticker bushes.
I am going to work on the video right now. Back in a few hours.
Very disturbing to see this damage in person.