Interesting thoughts from Steven Levy in What the Apple Watch Means for The Age of Notifications:

Done right, notifications are a wonderful Feed of Feeds, weeding out the stuff you really need to see from all the usual chaff in the stream.

But it’s hard to do this right when every single app wants to send you notifications. Even given that the system will limit itself to notices worthy of instant notice there are just too many notifications elbowing their way into what should be a narrow passage labeled, “Stuff I absolutely need to see.”

This decreases the value of all notifications.

Gmail has tried, but no one has really figured out the algorithms required to figure out what qualifies as “Stuff I absolutely need to see.” This is the holy grail of notifications at the moment.