I still think backlinks is really needed but you can read my observation here.
I bought 21 domains and possibly i have 16 up right now, with 2-5 posts. And i did some ranking analysis yesterday.
Website 1: Ranking on 30 pages for main keyword, 2500 monthly searches.
Website 2: ranking on page 2 for main keyword, 3.5k monthly searches.
website 3: page 18, 1k per month another keyword has 74k.
website4L page5, 2.9k
So, these website have no backlinks. Also, i saw many website which have many backlinks are really low in SERP. So, i think intellegent keyword analysis will be the key for success in futures internet marketing. Also, on page optmization is another key to rank high as compared to authority sites.