1. A computer-implemented method for determining active topics, comprising: receiving, at a computer system, topic information for a document, the information including at least one topic and a weight for each topic, where the topic relates to content of the document, and the weight represents how strongly the topic is associated with the document; receiving user activity information for the document, including a user activity value including at least one of a number of viewers and a number of editors of the document; generating and storing a topic intensity for each topic by multiplying the user activity value for the document by the weight of the topic in the document; monitoring the topic intensity over time by comparing a short term average of stored topic intensity values to a long term average of the same stored topic intensity values using a short term average/long term average (STA/LTA) approach; generating an alert based on the topic intensity; and outputting the alert if the comparison exceeds a threshold topic intensity.