Now that I think about it, I hope they figure out exactly what those blobs are- because they aren't unique to Camden. I see them all over the sidewalk in San Francisco, and I recall seeing them in other cities as well. Look for them in urban areas, I bet you'll find them too. They're not on the roads, mostly on the sidewalk, though I've seen them, rarely, on that yucky carpeting found sometimes in BART trains and school classrooms. It's one of the unasked mysteries of civilization, that no one really pays attention to (the only reason I remember is because I wondered what they were when I was a kid.)
My current theories are a) tree sap; and b) ... you know that really thick, disgusting phlemy gunk that gets hacked up by smokers, that's half spit and half tar? Well, what if it collects dirt and turns blackish and becomes those strange black spots? It certainly fits the location profile- sidewalks in urban areas where no cars drive, and smokers or bums would hack up #$%@! The crummier the area, the more spots, too...
Yeah, it's a lousy theory, I know- but do you have a better one?