Here is a well-known, but little used fact: People like free things. If you went to a street corner and started handing out staples, people would line up to take them from you. This is true even if you were giving away something they dont need. If you told them the staples cost $2, they would feel proud of having snagged one for free.
Now what would happen if you gave out something that people actually wanted, that they actually wanted to pay for, even stand in line for. In fact, we assume that if something is given away free then it must be inherently invaluable about it. When we receive something that we know has value, either in dollars or in its interest to us, we not only remember who gave it to us, but we actually feel indebted to them.
Seth Godin is the author of an amazing book called the ideadvirus. In that book, to simplify, he states that in order to quickly spread a message (virus), one needs to give something of value away, make it significant enough that others spread it on your behalf, and if the message is virus-worthy it will quickly spread through a group without much work from you. How can you profit from this? Read the book. To illustrate this,...