You need to file a DBA (Doing Business As) to take advantage of some of the tax benefits of owning a business. You have to file for an LLC (Limited Liability Corporation) if you want to get any of the liability protection. Most people don't file for a DBA or an LLC unless they start selling a decent amount.
FYI: I am co-owner of an LLC that my business partner and I setup to do side computer work. We wanted it for the liability protection.