Server Certificate Signing Request Question

I am generating a CSR for Verisign (WiMAX) to support EAP-TTLS. Some of the examples I see use the -nodes switch when generating the CSR, and others do not. Is the use of nodes CA specific, or why would I want to or not want to use -nodes. I see that when it is used the private key will not be encrypted, but I'm afraid I don't understand the ramifications of that. Any help or a link to a helpful RTFM would be greatly appreciated. Ben