On the schematic for an Ibanez "Tube Screamer" there is a 100 ohm resistor in series with the output emitter follower:
The output impedance of this pedal is 1.2K:
It looks like RB has a negligable effect as it increases Zout to 1.3K
An explanation I've seen for this is:
To start with, the series resistance at the emitter limits the amount of drive available to drive an amplifier input (although not by much), and in concert with the series capacitor forms a voltage divider with the output shunt resistor and the input impedance of the amplifier plugged into it. This drops the available signal only a trivial amount, probably inaudibly so. (http://www.geofex.com/article_folders/tstech/tsxtech.htm)
Considering the next stage after this buffer is likely to be either a guitar amplifier or pedal with input impedance of approximately 1M ohm I don't understand why it is needed.