Absolutely. Even if you intend on keeping your business small and in the family, you could develop a reputation that draws people from around the country or the world. If someone else uses your trademark and it is not registered, you have very little recourse, even if that person or company's reputation is bad enough to sully yours.
Filing a trademark ensures that no one else can use your trademark or a brand new service or item you created, including a business name.
Keep in mind that filing a trademark at the state level does not give you the full protection that you receive when you file the trademark at the federal level. It is better to file it at the federal level, especially if you plan on growing your business to serve more states.