KISSmetrics tracks user behavior and conversions across devices to understand customer lifetime value. It anonymously tracks users, then aliases identities when users provide information like emails. This allows it to link actions from anonymous to named users, building a full profile of "John Smith" from when he first visited as an anonymous user through upgrading his plan. KISSmetrics uses this tracking to measure ROI by linking user actions like upgrades back to original search terms and referrers that drove traffic.