Currently, aside from Ignore, which applies only to the chat areas, there is no way to prevent contact with another user. Reporting someone for spam doesn't always have the desired effect, and there is no way to report an inbox message aside from forwarding a possibly doctored email to a most-likely overwhelmed Mod. Well, I find it rather pointless if, after you use the ignore function on someone, they still have full access to both your profile and your inbox. I think both would be subject to less abuse if:

a) The /ignore function were changed to apply a "blanket effect" to one's profile and inbox

or

b) There were a "Block user" button next to the user name in both the profile and inbox.

It might also be helpful to have a "Report Message" link in the inbox, if nothing else, that would forward the entire conversation; however, this would be subject to the same weaknesses of the reporting process.