New report from Demos and US PIRG:

In addition, the analysis found that just 132 donors giving at least $1 million were responsible for 60.4% of all the money Super PACs raised in the 2012 cycle.  $71.8 million of Super PAC money came from for-profit businesses.

This evidence shows that the first post-Citizens United election afforded corporations and large donors the opportunity to use their wealth to amplify their voices far beyond the volume of the average member of the general public - threatening the basic American principle of political equality - and they took full advantage.