On 17th October Google released their disavow links tool.
Webmasters now can tell Google which links to ignore. this is much needed since Google annouced that links can actually harm you and spurned a whole new industry of negative SEO (and less straight ‘reputation management’ companies).
Google’s Disavow Links Tool allows any webmaster or site owner to upload a list of domains or URLs, with the result that links from those sites will be eremoved from ranking algorithms within a matter of weeks.
Google are very clever, as they will be crowd-sourcing lists of bad link domains from the webmasters concerned about their SERP rankings.
As the negative SEO world that was created recently continues, webmaster will be keen to disavow dodgy links. Google will be getting lots of data from the webmaster themselves, so ineffect they are using the negative SEO industry to kill the traditional back link building SEO industry.
Google are onestep ahead, and getting clever and faster at damaging those that want to beat the SERPs.
Top advice is that you should only now consider any SEO effort as a short term expense, not a long term benefit, which starts to rais the question of ROI of SEO versus other methods (e.g. PPC, which of course is where Google actually want you to spend your money).