I once had Norton (the internet security suite) -- hey, don't blame me, I was young and naive back then. It came as "free trial" on a laptop, and I figured, hey, give a paid-for service a try for once. (There were already warnings against and bad reviews about it, but I haven't found them yet. In my mind, the name 'Norton' still had a high-quality ring to it.)
This thing would notify me quite often with something that read like "YOU ARE BEING ATTACKED RIGHT NOW!!!!!!". In the beginning, I checked up on the supposed actual threats. Invariably, they were harmless, just normal occurrences in networks (a great deal of them were just pings). After a couple of days, I just gave up and turned the notifications off. They were useless by giving so many false positives, very obviously by design to justify the existence of the suite.
Shortly thereafter, the stupid thing prevented me from saving (self-created, macro- and animation-free) PowerPoint presentations as I was just about to present at a conference, which is when I finally got rid of the thing for good.