The Flickr iPhone app is the most addictive app on my phone at the moment after Wanelo. The kind of app I'll start using and then blissfully ignore text messages and the outside world until I get my fill.
It's not because of the great photos my friends continue to upload there (Instagram owns that part of my brain now and isn't giving it back), but because of all the things collectors of vintage design, furniture, calculators, magazines, advertising, architecture, artwork, matchbooks, postcards, book covers, product packaging, candy and toys are sharing there. I don't use it to look at photos per se but objects. It's like the difference between inspirational images and products you can buy. An "upload-only Tumblr for collectors" was how I first thought to describe it (there's no reblogging). Now I'm realizing how similar the mobile experience is to Wanelo.
Because it's all that content plus the intense scrollability of the app, which is so important on mobile and currently lacking on the Flickr website. You can see a lot of stuff quickly on the profile and favorites views, where I spend most of my energy, using it like I first used Etsy and now use Wanelo: tracing back the people behind the things I like and seeing what else they like, then continuing on into infinity.