Tracking clicks, opens, and browsing behavior can help tailor content so people see offers that actually matter to them instead of random spam. But it gets unethical when users don't know they're being tracked or when data is sold or used beyond its original purpose. Good practice includes clear opt-in choices, easy opt-outs, and using only the minimum data needed, ideally in aggregated or anonymized form. Done responsibly, personalization improves user experience and engagement without feeling invasive. The real challenge is balancing usefulness with trust and control.