Theres been enough debates on if that happens directly as a result of massive spam linking but there is another angle that hasn't been discussed often that pretty much guarantees that massive backlinking will eventually lose power across many sites.
Here's how that works
Its a known fact that Google DOES penalize sites that link to spam and that the power of links from those sites deteriorates as a result. You may not be responsible for who links to you but you ARE responsible for who you link to . Sites that don't keep out tools like Xrummer (link spam bot but there are others) eventually get hammered by a good amount of clearly spam links. Google then identifies these links and if the number of spam links reaches an undisclosed level begins to lower the value of the links FOR EVERYONE using that site and the page in the search engine falls.
So the reality is that the more people use these tools the more likely the kind of sites that allow them will have less and less power for everyone else linking from that site . Thats why you may not see any big changes in the algorithm from Google. Eventually the links get less and less power the more over run a site is with spam links. This degrading power is already built into the algorithm.
This is one of the reasons why people who advocate using mass backlinks have to tell you to always keep building links. They don't realize that the more they build (as a group) the less effective the links become.
What can you do? Don't spend your entire SEO link building campaign focusing on the kind of links that are targeted by these mass spam links (forums are the most targeted). For one a lot of the links are removed by the forum masters and then those admins that allow their site to be slammed by spam over and over again will have less and less link authority to give.
Funny thing about it is the spammers are destroying the power of the links they live by and its all designed into the algorithm. Some will object. third party source needed? Fine
Here's a quick cases study from a third party source but its nothing that every real SEO professional doesn't know
Google Page Level Penalty for Comment Spam – Rankings and Traffic Drop
Build your links with balance not just for ease. Avoid alleged SEOs/backlink gurus that don't create balance in links and who are always pushing mass spam links no matter how popular they may be. Long term the strategy is on a deepening downward trend - by design.