What’s the risk of over-segmentation?

Complexity without proportional benefit.

When segments become too narrow, you create problems. Campaigns become harder to manage. Content variations multiply. Testing becomes impossible because sample sizes are too small. Teams spend more time building segments than improving messages.

Statistical validity disappears. A segment of 200 people can't tell you anything meaningful about open rates or click behavior. You need volume to learn.

Personalization feels creepy. When you segment too precisely and reference too much data, recipients wonder how you know so much about them. There's a line between relevant and invasive.

Maintenance becomes unsustainable. Every new segment needs content, rules, and monitoring. At some point, the system collapses under its own weight.

The goal isn't maximum segments. It's meaningful segments. Groups large enough to matter, distinct enough to warrant different treatment, and manageable enough to maintain. More isn't always better.