[seanp2k2]

While I agree with the difference, it should still be possible to block these types of ads with some kind of firewall. Unless the OS is blocking the blocking at a lower level (which I'd be VERY surprised by), something like Privoxy and using that as the system proxy for http[s] should be able to knock these out if they're loaded dynamically. I haven't tested this, so it would require some inspection and network monitoring to figure out what's serving these. Some hosts file entries may even be enough.

[opnitro]

I think that's different because you are subverted the OS's attempts to advertise to you. Most people are not willing to go to this level. Changing search engines is not subverting Google, it's just not using their product.