[Babcock_Hall]

In the case of ethanoic acid, the electrons that are brought in belong to oxygen.  Oxygen is more electronegative; therefore, it owns the electrons in this formalism.  In biochemistry and organic chemistry, it is natural to focus on carbon and look for reagents that oxidize or reduce certain carbon-containing compounds.  Besides the reference I already provided, there are some other resources one could consult:
http://pubs.acs.org/doi/pdf/10.1021/ed079p965
http://web1.uct.usm.maine.edu/~newton/Chy251_253/Lectures/OxidationLevels/OxiationLevels.html
Halkides CJ, Journal of Chemical Education 2000;77(11):1428-1432.  http://pubs.acs.org/doi/pdf/10.1021/ed077p1428