In classic marketing techniques, referrals are limited. You can ask your customers to refer you, but unless you're willing to pay them substantial referral fees, the odds that they will refer you are spotty. Human nature is that most people won't do something unless there's something in it for them. On the Internet, however, you can literally have armies of people referring you, and they might not even be your customers! All you have to do is know how to exploit the digital word of mouth.
...