This year we saw a bunch of things that Google went after. Spammy links, Popular Rental Networks (although ton loads still exist and work there is unlikely to be any as promoted as BMR was) , some kinds of content and last EMDs.
Got to notice the trend - basically anything IMers are pushing or using enmasse.
So whats your take? Whats next. For those who see the trends it can be important because if you figure it out now you won't be screaming in another few months or weeks. Heres my two guesses
A) tiered link building - Google doesn't need to check backlinks with a backlink checker. the data on every sites link profile is sitting on their drives in databases. Limiting the ability of any site (regardless of tier) that is being hit by mass spam links to pass on authority and/or PR would kill most tiered link building especially people using tools like SEnukeXcr, Magic submitter, UD etc. who rely on blasting links at their tiers
B) this is going to be difficult but I think at some point Google will want to go after the High PR Domain aftermarket. There are couple easy ways of doing it that I don't even want to say publicly on the small chance they get ideas from the net. They won't be able to deliver a death blow because Mozrank is out there and they can't control that but they can make life a little more tedious (if SEomoz decided to mirror the changes Google made then it could be even bigger trouble). The bigger long term problem for them would be how they avoid crawling and giving back credit to domains they took away. Nightmare to try and program an algo/crawler that doesn't as links across the internet are recrawled.
I'm making a renewed push to get what I want now because whatever you get before they change anything will stick. They can't go retroactively. Domain market will never go away but it could just be a little harder to navigate.
SO those are my two. What do you think is next to be targeted?