Scrum team size

Having worked with education and teams for more than a decade, I know something happens with a group when it becomes bigger and when it becomes smaller. I've seen some dramatic changes when you move from three to four and when you are more than eight. Then there are some gaps at 15 and if you're over twenty: there is no way you have one functional group. You probably have a number of unoffical groups.

The reason for me coming to think about this was a collegue stating that he'd experienced a successful scrum team consisting of 30 team members. I do not doubt they were successful, but I doubt they worked as group in the sense I see a group. And for example Jeff Sutherland have the same experience: larger groups works less well or has informal divisions. What is kind of funny is that when I gave class, I said the best group is more than two and less than seven: and that is the same size Sutherland recommends. And the similarities are many between education and scrum: the discussions and the group dynamic.

So, why do people want large groups? Division is hard: you like the guys and don't want to miss them. And it's easier to hide behind others. In a small group it's easier to see if someone doesn't understand or does not pull his weight.

Go, small groups!

And no, two developers are to few: I like the old arabic saying on why you should have four wives:
If you have one, you love her too much
If you have two, they will fight all the time
If you have three, two will take sides against the third
Four is optimal
You will probably not afford five