well, you gotta try the app to see its potential. Why do so many people use snapchat when you can send pics to friends already through imessage/whatsapp? Because of the interface.
Look simplifies the process of sharing links, pictures, and apps and focuses on sharing cool things, not starting discussions.
People post on snapchat because of quirky face pics and time limit feature. It keeps people updated with others moods and well- yeah mainly weird face pics. You can send the same pics through iMessage, but not with the time limit feature. Just think about in real life. If you and your friends are being goofy and hanging around, one of you might make a quirky face or pose for a second, but they wouldn't hold that pose forever.
Your app has a great design- really simple and easy to pick up. But when people find links they want to share with their friends, they can send a text message, share it on Facebook, or even on Twitter. I don't think people are as interested in having an app just to share links, but I think you have a solid foundation to do something cool. Rather than targeting it for friends to share links together, try and make it into a idea sharing bulletin board sort of thing. I see you have groups as a feature already. If this was an app where I could add a bunch of people to join a group and then we could all post links, notes, pictures, messages, etc. in the group feed, that would be great! However, this is just my feedback. You saw the vision for the app, so it's your choice to try and take it where you want to go.
This is why I need Y Combinator. Because I know there are features I can add/subtract from the current app. However my vision is and always will be in tact: share cool things and talk about them.
Look simplifies the process of sharing links, pictures, and apps and focuses on sharing cool things, not starting discussions.