I suspect (OK, I'd like if) someone will release a spamassassin/dspam variant targeted at ads as a proxy, optionally with some distributed Pyzor goodness thrown in.
In an ideal world, it would be open-source and locally-installable, a la Privoxy.
In a slightly-less-than-ideal world, it'll be hosted somewhere "out there". It will probably be wonderful for 6-12 months, then bog down as everyone starts using it, then the site owners will use it to start serving ads themselves. At which point their only hope for any kind of redemption will be if they've called the service some variant on 'samsara': http://en.wikipedia.org/wiki/Saṃsāra
In an ideal world, it would be open-source and locally-installable, a la Privoxy.
In a slightly-less-than-ideal world, it'll be hosted somewhere "out there". It will probably be wonderful for 6-12 months, then bog down as everyone starts using it, then the site owners will use it to start serving ads themselves. At which point their only hope for any kind of redemption will be if they've called the service some variant on 'samsara': http://en.wikipedia.org/wiki/Saṃsāra