After discovering that the G1 had a hidden proxy configuration that allowed all internet traffic to be routed through a proxy of your choosing, I decided to dust off the old Internet Junkbuster, an Adblock predecessor from 1996 or so.
Like Adblock, Junkbuster allows one to specify via regular expressions a list of URL conditions to treat as advertisements, replacing them with 1-pixel transparent gifs before they get to your browser, effectively blocking any sort of unwanted intrusion into your web experience.
I tracked it down, compiled it from source, and got it running on my Dreamhost account. After configuring the G1 to use it, I found that it worked amazingly well. I fed it the current snapshot of the community-maintained "filterset.G" blocking rules, and banished ads virtually entirely from my phone. Awesome.
Until, that is, Deamhost's Abuse Department dropped me a line asking if I was aware that copious amounts of spam were being sent by my account, and notifying me that they were able to track all of the spam messages to my running Junkbuster installation.
I haven't yet investigated to determine whether Junkbuster itself has been compromised by spammers or whether it's just badly coded so as to allow this sort of abuse, but the discovery of my active installation and subsequent spam messages that were resultant from it happened within hours of me turning it on. Startlingly fast, in fact. I'm not sure there's really any explanation other than Junkbuster itself now containing malicious code, but I'll be looking into that shortly.
Either way, finding that the tool you're using to remove the spam from your web surfing is, in fact, resulting in spam showing up in the email of strangers is delightfully ironic.