It's not necessarily water itself, it's water that is safe to use, something that in the developed world, we generally take for granted (though we really can't anymore, considering the ongoing California drought and the coal ash and chemical pollution incidents in major water supplies in North Carolina and West Virginia, respectively). We turn on the tap, and there it is. The thing is, in many developing countries, there already IS a water crisis, especially among the poor, who do not have access to a safe, clean and steady supply of drinking water. 1 in 7 people without access to safe water worldwide amounts to 1 billion or more. That's not a small amount, but can be difficult to really get in places like the US.
Now, private companies being the source of the problem? I wouldn't say they are the only source, but I'd say their actions are one factor of many. The fact that they take water from one area (often in developing countries where there are water access problems) to make their products and ship those to other places (though not always…again, in a lot of developing countries, soda is cheaper than water, which is a factor in obesity among the urban poor) is not necessarily a good or fair thing, especially if you have a lot of people without access to safe water. And here in the US, fracking consumes MASSIVE amounts of water, and after it's used, it can't be recycled. Like many other issues, this is a very complex thing with a lot of factors but to pin it entirely on private business is premature at best. It's ALWAYS multifactorial. You can't blame the California drought on private businesses, for example. But around the world, other factors in lack of safe water access include poor sanitation, overpopulation, population density and climate change.
I think this link provides a better snapshot to the whole thing:
http://www.un.org/waterforlifedecade/scarcity.shtmlIt isn't a problem of there not being enough water. It's a problem of access and distribution from a combination of natural and manmade factors.