1. Any specific suggestions out of curiosity?
2. Realtime Digg is not really unique, if you have any other suggestions, lol I would love to hear them because it takes me forever to think of these things, and I really want to involve intelligent people like yourself in the building process.
3. If I remove the login requirement, don't you think it could get way too chaotic, and invite spammers to have their way with the site?
I strongly suggest you to(at least temporarily) remove: Display of people online, all the sorting buttons, the red in yellow notification, the need to sign up or login, the amount of views per post. Next to each post, only show amount of viewers, don't discriminate between guests or users.
After you have done this, start working on color-schemes, and read online guides on typography to make the interface less confusing and complex. Make sure a visitor's eye is drawn towards important elements, and that less important elements are in the background more ( smaller, less bright typography/elements).
2. If realtime Digg is not unique, why create one? It doesn't matter if it's unique or not, as long as your users get what you are offering them. "Interact with Others" is a slogan that could apply to an alcoholics anonymous group or a dating website. What does your website do that is appealing to me, in a maximum of 5 words?
3. Your first and foremost concern right now is to get users, if the site gets too chaotic- at least it will be used. In the event that you start to get serious spamming issues, you are most likely successfull already and you will have plenty of time to fix the problem. Don't think that far ahead.
Cheers, -Edo