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.
Consumers, like friendly trolls, are fickle and may prefer to be anonymous and have freedom to choose products and services or whatever brands, and change these choices at whim.
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.
A more balanced view suggests that trolls have uses, and may mostly be tamed, except, they will still bite you on the leg if you step on anything important in nature.
A friendly troll uses the regenerative capacity, for instance, mostly to fight sysopism and anarchize large public wikis. The world trolling anarchization encourages such behaviour within limits,