I don't see changes into social bookmarking and forum posting too. I think we have to pay more attention on new G+1.
You are mistaking .. if the links are discounted, it doesn't mean that the weight of a website or a brand in social networks isn't relevant ..
I think both quality content and backlinks are important. Everyone now starts to produce equally good content for their targeted keywords. The problem is, there are only 10 slots for 1st page. Backlinks will be the determining factor for the placing. Yet spammy backlinking will in fact kill your ranking instead of pushing them. So better do it correctly.
After Google' s Panda update the positive effect from Link Building has been reduced somewhat but what really matters is that you need authentic and relevant links coming back to your site from related websites instead of a link farm. Also article submission sites have their values cut down except that of Ezine articles.