Weak backlink profile = problem
Weak on-page content = problem
It isn't now really up for debate - you need both to make sure you are fine in any Google update.
However, the main problem is going to be with big sites and ecommerce sites with quite a lot of dupe/weak and thin content pages. Smaller sites and blogs should be fine.
It seems the "Panda" portion of the algo is calculated sporadically - which means if you are caught in it now then you won't get out for quite a while so any changes you make to your site are wasted.
All of you guys with one site or a panda affected site need to start creating new sites and fast. Forget "good practice" you really need to not be a victim and start treating Google like a game that you are going to win. Create loads of sites - even scrape your own content on new domains, try anything.