If you are not using PubSub to monitor new links to your customers' websites and the keywords (e.g. company and product names, check out my guide on HowTo Use PubSub) of your clients, you are not doing your job.
As the details of EMC's purchase of Dantz were being finalized, the PR teams for both companies were hoping to keep the secret until the moment they had decided to make public announcements. Unfortunately, their plans were leaked in an untimely slashdot article. This premature disclosure could have made a real mess of their PR plan if it weren't for the fact that Guillaume du Gardier, a member of the public relations team in France, was a blogger and had a PubSub subscription to mentions of EMC and Dantz. Because of his subscription, Guillaume -- not a regular reader of slashdot -- was the first on the EMC/Dantz team to discover the leak when he got the alert from PubSub... Once notified of the leak, the team was able to move quickly to regain control of the situation. Guillaume concludes on his blog that "PR Pro can't ignore blogging" I think he's probably also become a dedicated user of PubSub...
In an article on the EMC/Dantz story at SearchStorage.com, Curtis Preston at Glasshouse Technologies Inc., is quoted as saying that EMC acquiring Dantz would be a blow to Veritas Software Inc. Whether or not this is true, it probably would have been useful for someone at Veritas to have had PubSub subscriptions for both EMC and Dantz. These subscriptions would have allowed them to discover quickly that a significant change in the competitive landscape was about to take place.