Pros
The single best reason to work at Viacom is because it looks good on a resume. I worked with some talented individuals, but there was little to no sense of pride in anyone's work. There were opportunities to drink free beer, but not with the most talented minds at Viacom. The health benefits are quite good. Once every year or so there is free In'n'Out.
Cons
The environment was incredibly clique-oriented and much of the management is simply passive aggressive. The pay is lower than average while the stress is incredibly high, and the company's business models are not designed to reward good content--only good sales executives. Regularly employees are burdened with a ton of responsibility but denied agency and authority to execute creative solutions. Job titles almost never reflect the work done by the employees. There is very little interaction amongst companies. Bicoastal management is simply bipolar--the NYC and Santa Monica offices are almost never on the same page. Regular full-time positions are often axed completely, leaving the rest of the employees to pick up the slack when the jobs are never filled again, or, if they are filled, they are filled with freelance positions or unpaid internships. Some managers show so much animosity towards their employees that they often remark, "I don't have to say thank you because I give you a paycheck."