http://www.esia.net/Forms_of_Stalking.htm
Delusional Stalkers
They may have major mental illnesses like schizophrenia, manic-depression or erotomania. What they all have in common is some false belief that keeps them tied to their victims. Frequently they have had little, if any contact with their victims.
In erotomania, the stalker's delusional belief is that the victim loves him/her. This type of stalker actually believes that he is having a relationship with his victim, even though they might never have met.
The typical profile of a delusional stalker is that of an unmarried and socially immature loner, who is unable to establish or sustain a close relationship with others. They rarely date and have had few, if any, sexual relationships. Since at the same time they are both threatened by and yearn for closeness, they often pick a victim who is unattainable in some way; perhaps she is married, or has been the stalker's therapist, clergyman, doctor or teacher.