I really enjoyed this article because it happens to focus on a problem I'm knee-deep in at the moment, although I'm not ready to throw clustering out the window just yet.
There's a deeper issue which the author touches on, showing too much information on a map. This is possible independent of technology limits depending on what level of focus you wish each point to have. For many maps, showing a bunch of small points is an elegant solution, the map turns into more of a data visualization. But a bunch of points tells you very little about a particular thing. It is rich in aggregated information and poor in specific information.
If Google Maps just gave you a bunch of points instead of labels, it would be less functional. Every city would just be a large collection of points. Great, that might be interesting if you want to visualize how the locations are distributed in the region, but you are probably looking at the map because you want to find a particular thing.
Clustering is the natural choice: show the most important thing out of all the points in the area. A label is important, a big circle with a number in it is the worst out all the options discussed. My issue with Google Maps is that there is no visual indicator that there are other points there, and that seems to be largely driven by the fact that it is a marketing platform.
I'm working on a map that uses a hybrid approach. Each map has a narrow focus and is tied to a particular community/interest: concerts, bear sightings, hostels, food trucks, whatever you want. For each point of focus, there is a label and a thumbnail. Showing a bunch of these all in the same place is a bad user experience, so it ranks them and shows the most important one, and the thumbnail is replaced by a number indicating there are other points of focus in the vicinity. Users can click on the item to get a side panel that shows a listing of all the points.
There are also other points on the map that are secondary to its focus, public transportation vehicles and other location points that the user can filter. These are displayed as little dots, similar to the example that the author provides. If you zoom in far enough, they become more than just dots.
In designing the user experience, I tried to make it like a map experience that you might find in a strategy game. Each focus point is like a unit that will bring up more information in a side panel. If there is more than one unit there, show an overview of the units. It's a work in progress, but I'm happy with the result so far.