Notifications of internet subscriptions, news feeds, email newsletters and the likes are the opposite of what they're supposed to be, because multitasking doesn't exist. Instead of being useful of how they provide one with information, they turn out to be a real chore. Not only do they make people feel like they have to be on the watch constantly to not miss any of the data arrived on their devices. They actually lessen the interest even towards topics that the user originally subscribed for, because they disrupt the attention from any activity the person is doing in the moment. Of course they can get annoying for the obvious reason of when the uploader of the video or the poster of the blog or website simply feels the need to keep churning out content, even when they don't have anything new, meaningful or interesting to say. But the real problem is that the brain is forced into switching way too often. It's tiresome and slows down cognition, and it can cause permanent alterations to the brain, in the form of lowering gray-matter density.