A friend is a teacher and regularly writes to her pupils' parents about their children. Thus she has Gmail Contacts set up with a record for each child that contains the e-mail address of one of their parents.
Problem arises when she is teaching siblings. In the
To: filed she might write [Child2]. Gmail notices that [Child2] has the same e-mail address as [Child1] and thus the e-mail goes out as
"Child 1" <email@example.com>. This makes it look unprofessional, like she cannot tell the two children apart.
Gmail, of course, allows you to record chidren's names within the parents record, but then you can't autolookup.
A related problem that I have found the solution for elsewhere in this site is when she wants to write to both parents. Seems the answer is to capture the e-mail address as
"firstname.lastname@example.org>, <email@example.com". Strange but effective.