Do Not Covet
Everyone knows that one of the Ten Commandments is "Do not covet" (Deut. 5:18). However, most people do not know how this works.
What is the difference between admiring another person's thing - perhaps even desiring it for yourself - and coveting? The Sages explain that the prohibition of coveting only occurs when you begin to plot how you could get it from the other person. Even if you intend to offer him a price way above market value, the mere planning of how you can make his property your own is a problem of "coveting." Of course, if he has previously indicated a willingness to sell something, there are no restrictions. But the Torah is very strict about something that is not on the market.
The idea is simple. We have to learn to respect the ownership of others to the point where we regard their things as completely and utterly untouchable under all circumstances. As soon as he puts the item on the market, it comes into our dimension in potential - but until that point, it is not even something to consider.
The Torah puts it very nicely: "Do not covet his property, nor his wife." His property should be as taboo as his wife. In the same way that no normal person would try to plot how to get someone to willingly give up their spouse, so too his property.
The Sages explain why: If you believe on any level that you have a right to acquire the property of another even though he is happy with it, then you do not have absolute respect for his ownership. And not having absolute respect for his ownership is a first step on a very slippery path toward dishonesty and outright theft. So the next time you read about a hostile takeover on Wall Street, think about the Ten Commandments.