Here's my 2 cents....
You're assuming that the regulations will hold up against the corporations like they would a single individual in our society. For obvious reasons, it doesn't take long for one regulation to turn into 100, and eventually, those regulations are employed from the Corporations through the government to lock out competition.
Your concerns about protection from Corporations are understandable, especially in these times, but the Libertarian philosophy looks at an earlier step, one that you've overlooked.
Without vast gov't regulations to lock out competition, if a corporation is engaged in market manipulation, consumer fraud, price gouging... whatever, there would be another man waiting in the shadows to steal the consumers by offering a better way. Understand that there's no way to completely eliminate the practice of people screwing people, but in a libertarian society, there would be fewer victims and the losses would be felt by both the victims and the perpetrators.
If competition from motivated and determined entrepreneurs weren't shut out of the system via regulation that increases the cost of starting and growing business, the issues that concern you would be few and far between.
Man, it's late here and I'm worn out. I am honored to discuss such topics with you, but remember, no system is perfect. However, that which maximizes freedom for the individual will allow the market to weed out the manipulation naturally.