If you have an idea and can't reduce the bus factor by getting other people on your team to co-sign it then it shouldn't be part of the project. That shows that either it's a bad idea, that you're not able to communicate it well, or that the other people are overly cautious. All of these things are good reasons why your idea would be too much risk.
If you can get other people on board then it's a very good sign. The bus factor is just a shorthand test for that.
I think the title is misleading, since its' just the author that thinks there is a problem with the "Bus Test." I thought it was going to lead to a study or even the results of some forum or panel. As onion2k says, if you can't get people to buy into your idea, then it fails the Bus Test and should not be part of the project.
If you can get other people on board then it's a very good sign. The bus factor is just a shorthand test for that.