A few thousand people have been testing a Twitter feature called @MagicRecs, which Direct Messages you when your Twitter friends follow a particular account, or interact with a certain tweet, in large numbers. It's a recommendation engine, and it's pretty good at telling you what people are paying attention to at the moment. Here's my DM history from Magic Recs. It's been surprisingly relevant; I clicked every one:
Now the feature is rolling out more widely, not as a DM service but through push notifications on smartphone. Basically, Android and iPhone Twitter users are going to start getting notifications — following this person, check out this tweet, etc. The notifications will appear in the same way that mentions or retweets do.
Twitter for Android and Twitter for iPhone users will receive recommendations via a push notification. As with any notification, you can change your settings at any time; you can turn these notifications off or on with the "Recommendations" toggle in your notifications settings.
Given Twitter's intention to go public, the first question that comes to mind is this: will Twitter start recommending ads via push notification, too? After Twitter sent a recommended Dropbox tweet out recently, which looked like an ad but wasn't, Twitter CEO Dick Costolo told Buzzfeed:
So, no. Also worth noting that Apple does not allow ads to be sent via push notification.