1. A system comprising: one or more processors; one or more data-storage devices; a data-collection subsystem that receives and processes messages sent from instrumentation contained in remote web-page encodings, remote applications, and other remote instrumented entities; and computer instructions, stored in one or more of the one or more data-storage devices, that, when executed by one or more of the one or more processors, control the system to process a next message received and processed by the data-collection subsystem by: receiving the processed message from the data-collection subsystem; when the processed message is sent by instrumentation in a computational context from which another message of a current user thread was sent, using message user-related information contained within the processed message, including computational-context-associated user-related information, to determine a user associated with the message; when the processed message is sent by instrumentation in a computational context different from one or more computational contexts from which other messages of a current user thread were sent, using message user-related information contained within the processed message other than computational-context-associated user-related information, to determine a user associated with the message; and associated the determined user with the processed message.