Exactly. Flickr and Tumblr are both primarily about the content - there&#x27;s no need to force users to login before they can explore.<p>Also Facebook, Twitter et. al are the wrong examples to be looking at - brands already so strong people will jump through hoops to use them.<p>If you&#x27;re Yahoo! - coming from behind - your brand and even the brands of Flickr and Tumblr aren&#x27;t strong enough to to require users login before they get to try anything. In the case of Tumblr you might get the _existing_ userbase from the web to come with you but you won&#x27;t succeed in growing that audience on mobile.<p>Examples that do use gradual engagement would be games. Clash of the Clans for example - a huge success on mobile -  let&#x27;s you immediately start playing without any form of identification. Many mobile games have strong social elements but they focus first on getting you engaged before requiring anything.