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even if they provide a avenue of risk. People have called in bomb threats via public phones, thus a "Dark side" of public phones...

By pointing at a "dark side" of email you imply that the anonymous services should be rectified. I won't put words in your mouth as to how to do so. Other agencies are working on that very issue. Wonderfully its under the auspices of the US patriot act, an act that has little patriotism and much government control.

Back to tracing, if the email leaves our borders then the email is traceable.
The level of effort to trace it is too much for a local PD, however the NSA and by extension the Dept. of Homeland security sure can.
http://en.wikipedia.org/wiki/NSA_warrantless_surveillance_controversy
I won't go to the level of conspiracy theory and say that interior email systems are compromised to this level though.