Adrian has written a short article enumerating many of the security threats that can be mitigated using asymmetric encryption. Click here to read Adrian's overview of the benefits of PKI
As Adrian goes on to explain, Public Key Infrastructure technologies can be used to attest the identity, integrity and confidentiality of information, systems and individuals.
Encrypting File System (EFS), Secure Messaging (S/MIME) and Internet Protocol Security (IPsec) are three incredibly power technologies that take advantage of asymmetric cryptography.
It's a suprisingly easy read and at only a couple of pages it's well worth a read.