As Firefox/Moz increase in popularity, you'll see them targeted more and more - but the targeting should still be @ Windows boxen, not Linux boxen IMO. A firewall with no server ports allowed should seal off most of the crap, and as long as you are at relatively safe sites, you'll dodge 90% of the crap. Still, the spyware industry will be trying to sneak something in at even mainstream sites, and it does happen from time to time...

The best way to browse the web these days is on a VMWare session, with a saved restore point you revert to each time. It's the only way to be sure.