Single-threading not considered harmful

No, it's sequential programming.

Actually, I don't see multi-threading as anything but handling single processes multiple concurrent times. It doesn't matter if you are talking about 5 services doing a single different thing in each or if a single service is setting up multiple threads to do the same process several times at once.

The problem is recognizing when a dedicated single process is the best answer to your problem or when multiple threads on the same server would be best. Generally, when your problem is data driven, the multiple thread solution would be better and when your problem is cpu intensive, a single thread dedicated to solving the problem combined with a data storage mechanizm so multiple servers can attack several individual problems concurrently may be the way to go.

This article seems to cover the situation where one of those solutions fit and therefore it becomes the "best" solution for every situation. It doesn't seem to apply to dumb coding mistakes that make good design go bad. For instance, I saw one case where it should have used "-" instead of "+" in one place of a mathematical equation. It took me a week and a half to convince the manager there was a mistake in the equation.