There's an unofficial law in movies and other media that the strength of an individual ninja is inversely proportional to the number of ninjas present. In other words, a single ninja poses the same threat as five ninjas since each of the five ninjas has 20% of the strength of a lone ninja.
I saw a similar principle at work today while I was decorating a room with a group of people. There were about twenty people working but we probably weren't twenty times quicker than a single person decorating would have been. I suppose the need for communication is what slows down group work compared to individual work.
That said, I think we did a much better and quicker job than any one person could. Unlike movie ninjas, each of us was unique and had different ideas and skills to contribute. I'm often inclined to do things by myself, but not working with others can only be damaging in the long run.