Their demo makes one thing obvious, however. Douglas-Peucker just doesn’t cut it for topologies. This becomes a non-issue with a pixel-level of detail, but just looks bad in their demo. Their implementation doesn’t seem to preserve existing points between zooms; it’s probably just as efficient this way.
Read about it and then view the demo. When you think about the performance here of the polyline data set with 50,000 segments in it you really start to see why this is impressive. Vish has even more thoughts on the project.