I've started using an iPad running OnLive Desktop when I need to go places on the web where I should really know better.
The iPad is pretty much immune to anything currently out there, and the OnLive server instance I have is locked down and it's system files can't be modified so it's pretty much immune too. I believe the OnLive images are killed and rebuilt every night anyway.
I admit it's not a replacement for a full PC setup, but I'm rapidly finding it my go-to solution for most things Internetty. Doesn't hurt that it gives me a 97Mbit download speed AND because the OnLive servers are based in the US, I can get Hulu and ABCPlayer wherever I am in the world.
Downside; you do need a decent internet connection to connect to OnIive, so not a permanent solution for most people.