Karl Marx and Adam Smith both realized that there have been benefits to the division of labor, but Marx believes that through strict specialization, a person is being individually hurt by being devoid of greater experiences. A repetitive task makes a person seem more like a machine than a human. .
Smith notes in his "Wealth of Nations" that the division of labor betters society. Things can be produced more quickly by a greater number of laborers specializing in a single skill than by a single worker attempting various tasks. This one worker may not be completely apt at all the components to complete the entire desired product. A larger number of workers that can each be well adapted for a certain part of the whole product would be much more sufficient.
Smith states the now famous example of the pin makers. Smith once saw a small manufactory with a few men attempting to each do three different operations, but each man could only manage to his task slowly and inefficiently. (Smith, 5) However, once an individual can master a certain part of pin making, therefore doing his part and allowing his fellow workers do what they know to do best, production rapidly improves and speeds up.
Marx speaks about the manufacture of materials. Specialization does indeed quicken production, but it also has a negative point. The manufacture through the division of labor is "a productive mechanism whose organs are human beings." (Marx, 457) What could otherwise be a group of interesting individuals have become nothing more than a machine.
Smith makes his example very specific in explaining that each person does one job and only one job. If each creates the greater part of the whole, then it will be beneficial. Marx explains how this can come to be. He states that one capitalist may employ a few men who are all skilled at a certain craft (he notes the craft of making paper, twain, or needles, it doesn't matter which craft), that may each still be doing their usual work and producing single products each.