A friendly troll is any troll who happens to be in alignment with the goals of the system. Such a state of affairs is fostered in consumerium by being a troll-friendly system, which respects due process.
According to the Dungeons and Dragons Monster Manual, all trolls are stupid and dangerous. They can only be killed by fire or acid, and if a part of them is cut off, they not only grow the part back, but the part grows the body back. See w:Wikipedia:sock puppet for more information on this regenerative capacity.