I've never been masturbated by a machine. I would think that to be masturbated by a machine that Mistress had control over would be quite humiliating. Under these circumstances she could dictate both pleasure and frustration with a high degree of detachment. It could lead to scenarios such as her flipping through a circular with the sales at Macy's while I'm begging profusely for the machine to be turned back on. Many other humiliating scenarios are possible.