-High turnover itself is a constant problem: competent people leave or are mysteriously fired and replaced with fresh college graduates to take their spot. Lots of lost time on training, errors by newbies put team leads in awkward places. Clients expect perfection that can't be faked with 20 hours of hurried training.
-Pay is low, even for traditionally better paying roles like web developers or account directors.
-Management and company hierarchy is murky at best, totally broken at worst: you're never sure who you boss is or who you're reporting to. Employees report to mysterious sub managers who report to team leads but the team lead is tasked with evaluating employees.
-High expectations coupled with low pay lead to working a lot for little compensation, in turn affecting morale. While the employee handbook states that 40 hour weeks are standard and that overtime should be cleared with team leads, many people work long hours to get their work done without this.
-Politics and lack of formal HR dept. results in uneven punishment/reward for employees. Passive-aggressiveness hampers direct, in-team communication and leads to occasional animosity and gossip. Work review process can be painful and nitpicky - superiors will ask you to go back and fix extremely minor typos when reviewing work leading to workflow disruption, distraction and sometimes bad blood.
-The actual work is generally thankless, free of ownership, plentiful and relatively boring and repetitive. Revolving door of clients, coworkers and company policies makes workers feel insecure about their future with the company, hurting morale and productivity. While this is hard to beat at a marketing company, its exacerbated by long hours and other company shortcomings.