Every so often I'll try to switch to two spaces, but I fail. Four spaces magically fits the length of `var `, and allows for nice variable alignment which is too good to pass:

    var one = 1,
        two = 2;

    // or
    var one = 1
      , two = 2

I also feel that when you have deeply nested callbacks, two spaces are not enough to visually separate indent levels at a glance.