Work Opaqueness: The larger a Circle is, the less accurate your team member's assessment of each other may be. Members tend to be the MOST familiar with the teammates' work they interact with the most often.
Various Areas of Expertise: Members do not always have experience with the effort required of all disciplines within the organization. For example, A developer may not know the rigor required of a marketer managing an active campaign. Due to this lack of experience, they may tend to under allocate to members of the marketing team.
Recency Bias: Members tend to allocate based on their recent experiences. If your Epochs are too long, members may forget about work completed at the beginning of the Epoch.
Process Fatigue: Every Epoch requires your team to record contributions and allocate them to team members. If you have a large circle, the frequent allocation could lead to burnout.