Actually the code does limit the number of recepticles that can be placed on a circuit. A 15 amp circuit is 10 and a 20 amp circuit is 13. This is based on 180VA per common bus on each outlet. Therefore, you cannot just add an outlet just because you need one. See below:
220.14(I) Receptacle Outlets. Except as covered in 220.14(J) and (K), receptacle outlets shall be calculated at not less than 180 volt-amperes for each single or for each multiple receptacle on one yoke. A single piece of equipment consisting of a multiple receptacle comprised of four or more receptacles shall be calculated at not less than 90 volt-amperes per receptacle. This provision shall not be applicable to the receptacle outlets specified in 210.11(C)(1) and (C)(2).
