Several factors helped structure the outcome in this case (the most interesting being the SG defending the point that the government could ban corporate-sponsered print media before an election during oral arguments), but in the end this case was about the Court's assessment of the limits of free speech rights--given that the Court has extended other 1st Amendment rights to corporations.
Kennedy's majority opinion speaks about the slippery-slope (that regulation of corporate speech could lead to government regulation of blogs and the internet), and Volokh talks about how this decision will simultaneously secure the media's liberty while diminishing their grip on elections as other types of corporations flood the market of political speech with their views.
While reading his dissent from the bench, Stevens echoed the Thurlow-esque argument against corporations as people (relayed here by Dahlia Lithwick):
Stevens hammers, more than once this morning from the bench on the principle that corporations "are not human beings" and "corporations have no consciences, no beliefs, no feelings, no thoughts, no desires." He insists that "they are not themselves members of 'We the People' by whom and for whom our Constitution was established." (link)And I'll bet Kennedy wondered if Stevens was going to engage in the slippery-slope logic that he had just railed against, and suggest something to effect of "well, if corporations are people, does that mean they get to marry or vote?"
In the end, the schizophrenic US legal system will always have contradictory protections and limitations due, in part, to the preferences of those who shape the rules at one point or another during the political business cycle. Corporations are recognized as juristic persons and have (now) been afforded most of the other legal rights of individuals (except some natural rights like freedom of religion), so we'll see how taking down the PAC middleman impacts corporate influence on elections.
In this case, the focus shifted from the Clinton Video-on-Demand to an assessment of corporate free speech; however in some other nations, corporate spending regulation has been debated on other fronts. Comparative research has shown that corporate spending limitations spur increased levels of electoral volatility and the proliferation of new parties. In some nascent democracies, such as Postcommunist nations, state subventions and electoral regulation of corporations have shown some success in reducing party volatility & enhancing party institutionalization (or at least that's what I found in this article with Joseph Robbins forthcoming in Party Politics).
However, this brings up an interesting non-free speech ramification of the Citizens United case...how will this impact the preference heterogeneity within and across the national parties and their elected membership? If this decision begins to dismantle similar laws at the state level (which I am guessing it will), it would be interesting to observe any trends in party preference alignment and electoral turnover if corporate spending floods (or dominates?) the market of political ideas--assuming corporate preferences are really different from the current political mainstay.
I doubt they are because they've already been using PACs to get their message out, and corporations are still beholden to shareholders & the market; furthermore, this probably changes the mechanism of corporate campaign financing, not it's purpose (corporate money still made it into the hands of politicians, and likely influenced votes (or not), but now those donations will be a [slightly] more transparent). I guess I am more curious about the wealthy, far-from-center companies that might try to dominate the political message in an election or how this opens (another) door to foreign interests with a stake or influence on corporate donors.
Because this case examines free speech, one of the plaintiff's arguments introduces the question of whether this regulation of the film's financing is subject to strict scrutiny (requiring that the restriction involve a compelling interest and be narrowly tailored to meet that interest). In the past few decades, as cases reviewing 1st Amendment rights are more narrowly ruled upon, less often argued in front of the SCOTUS, and the jurisprudential regime of the Court has changed--it seems that the concept of strict scrutiny has come up less and less often. Here's a visualization of the number of times it has come up in written opinions in the past couple of decades. This compares the SCOTUS, all federal courts, and the 9th circuit court (because the 9th is always interesting)--it doesn't control for the volume of cases, types of cases, or characteristics of the sitting judges/justices, etc...just a run-of-the-mill frequency:
As an aside, the word "orthogonal" was used in oral arguments a few weeks ago. Scalia & Kennedy were smitten with the word & I think we can expect to see it show up in the written opinions for Briscoe.
Murry Hill Incorporated Running for Congress -- because corporations are people too.