Jeff Lash on Focus Groups

On his How to Be a Good Product Manager blog (which, I might add, is a great read and off to a roaring start), Jeff Lash advises against reliance on focus groups:

While they have their place, focus groups are too often overused and misused.

Executives are often enamored with focus groups. In most cases, however, your product manager should avoid them and employ other market research methods.