[Consultant32452]

Private citizens and corporations can't accumulate much power without the government. Think of the most evil wealthy American citizens and corporations you can think of. How much money would they have without trademark, copyright, or patent protections?

[jandrese]

Like water barons, warlords, feudal guilds, etc?

By what mechanism would a libertarian put a check on the capital's natural tendency to accumulate wealth and power upwards?

[Consultant32452]

I already answered your question, by dismantling the government provided mechanisms by which wealth and power accumulate. I'm not an anarchist, not even a minarchist. I'm not even opposed to some manner of minimal intellectual property rights. The point of bringing up the concept of zero intellectual property rights is so that you can see the primary mechanism people accumulate wealth and power in the modern age is through government created mechanisms such as patents and copyright. Since I'm not an anarchist, hopefully you can see how it's trivial to protect from things like warlords.