Should a subject in a memo be all key in all caps?

In a formally typed memo, typing the subject line in all-caps is improper. It is a common practice, however, so you may do so if it looks more "right" to you. The only time in a formal document that I use all-caps is on the "Objective" line on a resume. In that case, the line contains only the Word Objective in all-caps and the title of the position, also in all-caps.