In one of the current games I am running a PC carries a Firewall infomorph hacker. The poor guy suffers from Cotard's delusion and thinks he is dead. He is not entirely wrong, since he suffered some extensive brain damage in the Fall that was patched as well as Firewall could, but still messed up much of his identity. So now he is a kind of sad ghost Firewall uses on missions when not giving him therapy. He obeys his host, since obviously his host must have captured his soul here in hell... (exactly the kind of travel companion you want when going through the White Zone ;-) )

It would say it depends very much on the skill and how it is applied. Standard muses are purpose-build for accounting and psychotherapy, so I would say it follows that they can be used to support the Player Characters in such tasks, or perhaps, the other way around. Likewise, a muse should be able to offer support in any field it has active skills in; Hardware: Electronics, Infosec, Interface, Programming, Research, Perception and three other knowledge skills because the muse has, literally, been programmed to offer assistance in those fields. However, in order to offer a teamwork bonus, I think it is only logical that the muse must be [i]capable[/i] of offering that +10; aiming and firing small arms or disposable launchers is probably not something most muses have been built to do, and it is unlikely that they'll be able of offer support in those fields any more than a character with mesh inserts is capable of helping themselves. In fact, p. 264 states that muses are not capable of defaulting, which I take to mean they are not [i]capable[/i] of performing actions outside their skill-range; I do not think it is a far leap to say that the actions a muse can support a character in limited to their chosen skills and the most mundane and effort-less mesh-actions. Exactly which skills a muse should be unable to support a player in making I'm honestly not sure, but I imagine that if it's a skill the player has put any points into at all (for example, Pilot: Groundcraft) there's not much the muse can support a player who knows how to drive. Additionally, taking a clue form the infolife background, a standard muse is probably very deficient in social situations, so it can't offer much support there beyond researching the topic and providing summaries to its owner. So, in most cases I'd say no.

I allow it in my games. Then again, I too ruled that you can only aid someone in a skill if you have it as well, which restricts what skills a Muse can help in.