Unveiling network and service performance issues in complex and highly decentralized systems such as the Internet is a major challenge. Indeed, the Internet is based on decentralization and diversity. However, its distributed nature leads to operational brittleness and difficulty in identifying the root causes of performance degradation. In such a context, network measurements are a fundamental pillar to shed light on and unveil design and implementation defects. To tackle this fragmentation and visibility problem, we recently conceived mPlane, a distributed measurement platform that runs, collects, and analyzes traffic measurements to study the operation and functioning of the Internet. In this article, we show the potentiality of the mPlane approach to unveil network and service degradation issues in live operational networks, involving both fixed-line and cellular networks. In particular, we combine active and passive measurements to troubleshoot problems in end-customer Internet access connections, or to automatically detect and diagnose anomalies in Internet-scale services (e.g., YouTube) that impact a large number of end users.