[nugget]

Google runs the largest advertising network in the world. Plenty of malware slips through the cracks every day, both downloadable apps/software/extensions as well as ads that lead to obvious scams. Facebook, Microsoft, Yahoo etc all suffer the same problems. I think these problems are likely unavoidable at that kind of scale. But I would never rely on these companies as the only (or even primary) line of defense.

[floatboth]

Of course the primary line of defense is not running random crap executables.