Digg Question (noob question)

So I went to Digg.com and thought I'd go ahead and blast my site on the page there and did. I noticed that people had votes; and was wondering a few things. Anyone who advertises or uses the site, please input your thoughts on the matter.

1. If you create a link, is it worth building backlinks to that link?
2. If you create a link, why would you want to have "votes/diggs".
3. Why is it that on the home page right now I'm showing the 3rd from the top having 20 digs, whereas the ones throughout the site have higher digs? Does it not matter how many diggs you get to determine the top position on the homepage?
4. If on the home page, how long would it remain there?
5. Is it worth buying diggs from these providers if so why?

I've been doing extremely well at SEO - but haven't looked into the details of digg just yet. Any expertise on the matter would be greatly appreciated; thanks in advance.