That’s not exactly true although it is likely to happen. I won’t go into details right now (too long) but something that it is useful and it is a real benefit for the forum members, will stay.
Personally, I think that your approach is wrong (and it happens to many people coming from India so I guess marketing information there is not up to my standards)
So why do I think that you’re approach is wrong? Because you only think about do follow links, you talk about rank, you talk about social media and how to use it… or more to say it… how to abuse it and take it beyond the limits.
You say that DIGG is bad because the links are no follow?
Simply, to me, it shows that you do not understand the medium.
Social media is the new word of mouth. You’re not the one to share anything there (more than whatever you post in you FB page or your pinterest). It is the people who shares because your content is that great that deserves to be shared.
If the links are follow or not… It is just that important, you can still have a huge amount of traffic from DIGG and that’s what Google loves more than do-follow backlinks.
Sorry and maybe I’m sounding a bit harsh but you make nonsense to me