Perhaps I am partial, but I would say absolutely. While I do think you could get away with it, it sets the tone for all employees and really helps manage expectations on policies and procedures. I would highly encourage you to put one together, even if you pulled a template off the internet to start with.
Key components you may want to include:
1. Equal Opportunity Employer
2. Hiring Policy - typically have a three months test period.
3. Personal Conduct
4. Dress Code
5. Communication policy (phone/email)
6. Internet use policy
7. Health and Safety
8. Harassment
9. Performance Policy
Make sure that all your policies comply with state and federal requirements.
I also think its a great idea to ask your employees to take a look and think of ways to improve it.