In my project they've decided to use 3 spaces as indentation. I actually think 3 is pretty optimal; 2 is too little, 4 is a bit too much. Unfortunately it is tempting to some to set their IDE tab settings to 3 spaces, which is just wrong! Tabs should be set to 7 spaces!
Why? Because that will make it really clear where they are used, so they can be eliminated.
