University of Copenhagen has an AI project on "conversation-mediated assistance", where agents performing this assistance are created based on metaphor of "ghosts" (Overview, PDF). As the paper explains,

The notion of ghosts has been chosen because of traditional characteristics of ghosts found in the popular literature and in folk tales:
1. Ghosts are mostly invisible or only vaguely visually manifested
2. Ghosts are often bound to a specific location which often has a very special relation to the ghost
3. Ghost owe their twilight status to some unfinished business and they are therefore active and striving
4. Ghosts only appear when called upon or if they feel an urge to manifest themselves

These features are heuristically very interesting for developing functionally satisfactory agent based assistance while keeping the technical requirements at a minimum.

Mark Liberman on Language Log comments:

After a brief scan of their site, I can add some other characteristics of ghosts that are useful from the point of view of system designers:

1. Ghosts are not always helpful or well intentioned.
2. Ghosts don't always tell the truth (or even know what it is).
3. Ghosts are often annoying even when they are entertaining.

http://itre.cis.upenn.edu/~myl/languagelog/archives/000533.html

To prove Mark Liberman's observations, here is "Thin Lizzy" ghost personality outlines:

Despite keen celibacy the skinny and pale Lizzy died in an early age due to poor health. Being a former firm believer in a controlled lifestyle with vegetarian food, yoga exercise and refraining from male company her unjust death made her very bitter. Bodiless she has just acknowledged the true meaning of body pleasures and now she blames her former lifestyle for the untimely death. Lizzy mainly resides in the canteen trying to convince everybody to eat a lot of fat foods, meat, buying that extra piece of chocolate, drinking Coke instead of water etc. Many think that she is in conspiracy with the canteen owners, but actually she is on her own crusade, which is manifested when she interferes with any effort from the canteen to put more healthy dishes on the menu. At the slightest chance of romances, e.g. at parties, she is especially active in trying to couple students. Sometimes she goes too far in her eager revenge over her own former frigid life and digresses slightly into obscenity.

Microsoft Word's own ghost, a Paperclipus Vulgaris™, which pops up, winks, and claims that she knows better what I am going to write in my letter, can rest.

Yesterday I tried a new recipe for making bread. Two previous were Classic White and Mediterranean Herbed. They had flour, margarine, sugar, salt and yeast (Mediterranean Herbed also basil, oregano and thyme). I liked them, but not as much as the last one I made: Sally Lunn. My book said:

"Sally Lunn is believed to have been named after the Englishwoman who created this bread in her tiny bakery in Bath, England. The recipe was brought to the colonies and soon became a favorite in the South."

It is different only in that it has eggs. Not sure why it makes such a difference, but it tastes better. And thinking about how old the recipe is, I am feeling a little dizzy.

My next experiments will be Honey Mustard Bread (honey and mustard?) and Beer Bacon Bread.

When people think about totalitarianism, for some reason they imagine Siberia, Gulags (in plural), mountains of dead bodies... All these pictures are as alien to me as they are to you. But here is real difference, and here is real freedom: nobody there would ever think about using beer and bacon to make bread!