I'm not so sure that today's decision will lead to the doomsday scenario that's being predicted on all of the talk shows today.
The reason that I believe that this may not lead to a corporate take-over of the electoral process is that I doubt that many corporations will want to wade into the political arena especially those that sell directly to the public and are readily boycotted. What company wants to alienate 40-50% of their customers? The corporate boards making these decisions will also have to deal with alienating their employees and also how it might impact hiring new employees.
The argument against this is of course large companies that don't deal directly with the public and aren't well known or easily boycotted. However, almost all companies have at least an indirect relationship with the public which could be damaged by advocating for a particular candidate and they still have the employee issue to deal with.
I really believe that most corporations will not be willing to jump into politicizing their company. Heck, most of them have enough trouble running their day-to-day operations than to have to add politics to the equation.
I would also argue that most of the large corporations that want to be involved in politics already are involved anyway and not in a public or perceived partisan way (e.g. Goldman Sachs) so why would they want to "go public" and cause themselves more headaches?
I must confess to not having really dug very deep in trying to understand both sides of this case yet, but from what I have heard so far it does seem that this decision is "judicial activism" at is finest, yet where are all the conservatives screaming about the justices overturning decades of precedence? As I said, without further study, I am inclined to side with those against this decision giving too much power to corporations in our country, however, I am keeping an open mind until I get a chance to study the issue and the decision in more depth.
I guess what it comes down to with me is that I am much more afraid of hidden influences of big business on Congress (e.g. lobbyists) than on open and very public support of candidates.
I've put on my fire-retardant clothing, so please flame away and convince me I am being foolish.