1. Overall, fantastic idea. I would actually use this if you had an option to sign up with email address only. I think a lot of people might be uncomfortable with putting their phone numbers online that fast without a secure connection.

2. Make an option to have profiles private. Networking and social plugins aside, people might want to discreetly bookmark apps they find for various reasons.

3. I think one of your biggest challenges at this stage is implementing this for mobile machines. There is an easy way around this, coding a browser which will have the interface plugged in already. But I don't see many iPhone users doing that just to bookmark something, it'd be downloaded and rarely used, and eventually, deleted. Your best bet is integrating that function into the app.