Exploiting the online tools to re-route unwanted spam would only work for mail that has paid postage and been processed through the system. If you're using Informed Delivery you'll see that most of the "current resident" spam doesn't appear in your digest because it hasn't actually been mailed (it's placed in your box by the postal carrier directly). Would a named re-route hack work on the processed spam? I say 60/40 in favor of yes, until they catch on. Lots of magazines and catalogues tack on "or current resident" after the name and if the USPS routing regex is not too strict you'll either be able send all your Sears catalogues to Abu Dhabi or you'll discover an un-handled edge case and break your mail. Either way, sounds fun.

Are those services free in the US? In Canada forwarding costs quite a bit.