What data privacy issues exist around segment tagging?

Segment tags can constitute personal data processing under privacy regulations. Tagging someone as "high-income," "health-conscious," or "likely pregnant" involves making inferences about them—processing that requires lawful basis under GDPR and similar laws. Even seemingly innocuous tags like "inactive" or "discount-seeker" are data points about individuals.

Key privacy concerns include: sensitive category inference (health, religion, politics, sexuality—even indirect inference is problematic), profiling transparency (do subscribers know you're categorizing them?), data minimization (do you need that granular tag, or is it excessive?), and retention (how long do tags persist after they're relevant?).

Tags you create become data subjects can request. Under GDPR's right of access, subscribers can ask what data you hold—including segment memberships. If you've tagged someone "low-value customer" or "complaint risk," you may need to disclose and explain that. Build segments you'd be comfortable revealing. If a tag would embarrass you when disclosed, reconsider creating it. Segment thoughtfully and document your basis for categorizations.