Business Week has an article by Jeffrey Kaplan:
Myth #1: SaaS is still relatively new and untested.
Salesforce.com has been in business over five years, has more than 399,000 subscribers at 20,500 companies worldwide, and is growing at about 80% a year. NetSuite has been in business eight years, and company officials say it has thousands of customers globally using its online applications.
The oldest and biggest SaaS purveyor? ADP (ADP) — the world’s largest payroll application outfit — has been in business for nearly 60 years, generated $8.5 billion in revenues last year, and served about 590,000 clients worldwide.