Eric, the only thing that should really worry you is an ex-employee stealing clients. As others have said, starting a business is hard work, not anyone can do it. I think one way to prevent clients from following an employee is to keep the employees away from customers. That is, YOU should deal with all the clients personally. Develop a personal relationship with them. Ask them about their job, their kids. Become a buddy of sorts. Make them trust YOU and make them understand that your employees are there to help out, under your supervision, and you're doing the important tasks. If a client barely even knows your employees name, he might be less inclined to follow him should he leave and start his own business.
My old boss was like this. He got really friendly with most of his clients, to the point where he'd be invited over for birthday parties and such. He was a terrible detailer, but he had good people skills. More importantly, he didn't let me get close to the customers and never let them know that I actually knew more about detailing than he did. I don't know if he was worried I'd leave with his customers or what, but he had some really loyal clients, despite his bad techniques.