First things first, the basics. What is a trademark anyway? "A designation of origin, i.e. a brand that signifies the source of a service or product and its quality and good will." (Bloomberg Business). Pros of trademarking: If your business name becomes well known, someone else might try to use your company's reputation for its own benefits. A trademark protects not only your business name, but your logo and brand as well!
Cons: Often costs time and money, and many times involves lawyers (more time and money!).
Search your business name to see if it's already trademarked here: http://tmsearch.uspto.gov/bin/gate.exe?f=searchss&state=4806:89r2g1.1.1