Actually it looked more like insect eggs stacked tightly next to each other.
Kind of like this but more tightly clustered and brown: http://www.flickr.com/photos/54516384@N02/5374126714/
It actually remined me of the egg clusters that giant water bugs carry around only smaller and not as neatly packed.
I also saw it on some of the vegetation in my pond, I would find a stem that was wrapped all the way around with these brown clusters in a spot that was 1-1/2" long. The rest of the stem would be clean. Algae is pretty uniform in its coverage, this stuff wasn't.