It's obvious here that there are two entrenched camps. Those that recognize the utility of unions and those that wish to see them disappear. I, for one, grew up with a father that believed unions to be a cancer of the working force. He was a salary man in the automotive industry for his whole career (and is now retired with a good pension and benefits). Because of his own individual experience, he came to this conclusion. However, in his retirement, his tune has changed. He sees all the jobs that have been shipped overseas and realizes that in a lot of ways, it was industry that lobbied the government to keep import tariffs ridiculously low and it was industry that lobbied for tax loopholes that favored an 'off-shore' model, and as a result it became cheaper to manufacture goods and services overseas and ship them back to the US, therefore leveraging workers (i.e. unions). The result is more desperate workers working lower wages, a general dismantling of representation, and the ability for industry to render local labor obsolete in many instances.
The whole notion of letting capitalism ride unchecked, letting the market determine wages, etc, is ridiculous, because now you pit an individual against an organization. No matter how small, this organization (the employer) is essentially part of a larger organization large enough to manipulate the government in it's favor (If you think about it, these large corporations that lobby for favorable tax-codes and low import tariffs (that also benefit the smaller organizations) are very similar to a union and it's process of collective bargaining, except this union is made up of corporate personhood, not real individual personhood... but that's about as far as we need to get down the political aspect of this

). When you factor in the above leverage (and remove the laws associated with a minimum wage) you could essentially, pay a person no wages, if they agree to it. So for example, let's say you're a worker that comes from one of those countries where slack labor laws have allowed US companies to exploit cheap labor. You somehow manage to get into the US, the land of the free. You can't work here. So you agree to work for free, in return for an H-1 visa sponsorship. So now you're working for a company so that you can simply stay in the country. Well the employer realizes that since they're not paying this guy any money, that they would need to feed him, so they agree to give him room and board. Notice I didn't say health care? That's because employers can opt to take out insurance policies on you if you die, and in many cases, the payout for your death is worth more than the business you generate for the company when you're alive. The only difference between this and slavery, is that this worker can leave the situation if they want to (except they wouldn't be able to work anywhere because the H-1 visa sponsorship only works for that particular company so they are heavily persuaded to stay in this situation - btw this is happening in the US as we speak in industries like agriculture - but I do believe they are paid a wage (but room and board is deducted from that wage)).
So we can all see that the flaw of that hypothetical is that the dude is an illegal alien. We can all say that this dude is illegal and he shouldn't be rewarded for entering the country illegally, and this is his plight. But let's imagine if he wasn't illegal. Let's imagine if this same opportunity was available to him as a citizen. You have no job, can't find a job, but need a place to stay and you need food . If you eliminate minimum wage, and all the 'hand-outs' like food stamps, then something like this model becomes the market determined minimum wage, and you would perpetually have a segment of the population in servitude to some corporation. This becomes the entry level for self-imposed servitude created by a labor market created by the same organization structure mentioned above. If you start eliminating minimum standards for an employment agreement, you start venturing into situations that challenge human rights and dignity, because if you leverage the situation enough, you can create enough desperation to create a free, expendable workforce.
The United States created it's set of labor laws (including the minimum) wage to prevent situations like this (which was happening in the Great Depression), because the United States felt that it was a better, more humanistic country and that it should provide for it's citizens (including the poor - hell, this sentiment is even written on our Statue of Liberty). The labor laws, including the minimum wage, are part of the economic infrastructure that accommodates business. I see them as something that is just as integral as the system of public highways and roads that corporations utilize when doing business.
Unions, in my opinion will not go away, because there will always be a need for labor. As long as there is labor, there will be a need to organize. In fact, the more a government, or corporations pushes against organized labor, the more they incite the creation of organized labor. I love it when people argue that they don't need a union, or they successfully work in a company that does not have a union, because they fail to see that they are also organized. In most cases, their organization, the structure of their workday, sick leave, hours they work, days out of the year they work, etc are all the result of labor organizing into a voice to set forth certain demands at some point in history. You, and your collective coworkers might accept your working environment, but ultimately, if your company has set up at least some kind of minimal approach to fairness, safety, and wages, and you and your coworkers continue to work there believing that while it might not be perfect (no company is) that it is at least acceptable, then you are participating in organized labor. It has been you, and your coworkers that have decided this, either implicitly or more directly as an organized bargaining unit. This includes business owners and employers who have decided to adhere to the set of rules and laws in regards to labor (which essentially came from organized labor), or who have chosen to go beyond the minimum, because it is beneficial to their organization. Business owners choose organization, and in many cases businesses choose unions because they are the best organizations for their livelihood. Whether a group of employees choose to define things more clearly with a union depends of whether or not the employees see the need. Organizing individuals is the only way initiate large-scale change. I think Guitar Center should organize into a union. They obviously see a need. It'll be good for everyone, including the customers.
My two cents