1. A method comprising: training a usefulness prediction model to generate a usefulness prediction in connection with a given universal resource locator (URL), the training of the usefulness prediction model being based on a training set of URLs, a count of negative URLs and a count of positive URLs identified by the training set, and for each feature extracted from the URLs in the training set, a count of the positive URLs in the training set that include the feature and a count of the negative URLs in the training set that include the feature; extracting one or more features of the given URL; and using the one or more features extracted from the given URL and the usefulness prediction model to generate the usefulness prediction in connection with the given URL.