- Love love the basic idea.

- Focus on promotion.

- Get users, don't monetize until you're at least a year in.

- Don't launch features. Make your existing feature better (by keeping the creeps out, increasing its viral factor etc, all the backend stuff that's actually really hard, versus adding comments and likes, which is easy.)

- You can slowly add little interactions, but stay away from commenting, private messages etc for a loooong time, that's not where your value is.

- Again, don't add "standard" features like comments, profile pictures etc, since that will just dilute your positioning.