When the tech boom fell apart the % of Open Source businesses to fail was comparable to the % of proprietary firms to fail. This points to the flaw not lying in the business model. Here are some examples of successful businesses:

JBOSS

Producers of an open source servlet engine and J2EE implementation.

• Documentation
• Training
• Services

arsDigita

Web services company acquired by RedHat. Produced Open Source web community toolkit.

• Education
• Flat Fee Services

RedHat

World's #1 Linux distributor.

• Linux Distribution (sells CDs)
• Documentation
• Certification of Developers
• Training
• Build custom services on top of platform