There is value in the intellectual property of your business, and its worth protecting. Intellectual property can include your brand, any written materials, your experience, systems and processes and your customer database.
Just holding the company name for your brand is not enough to provide protection. All it does is prevent someone registering another company with the same name. To protect your brand you should consider registering a trade mark, either on your name, or logo or both. If you have trademarked your brand you can stop third parties from using or advertising your brand without your consent.
Any written materials (other than those specifically prepared for a third party at their request) are protected by Copyright Act 1994. Any materials created by your employees are owned by the employer unless specifically agreed otherwise under an employment agreement or other agreement.
If a key person in your business leaves or is injured what do you do? Firstly you can obtain key person insurance to ensure you have some funds coming in if your key person is injured and unable to work. If you are hiring someone who will be a key person you should consider including a valid restraint of trade in the employment agreement.
Your employment agreement should prevent previous employees from approaching customers on your database.