The patents that have been discussed in this forum suggest that Google is going well beyond "putting out fires." And, as a practical matter, it makes more sense for Google to develop "scalable solutions"--and to see how they work in an organic search envirnoment--than to play whack-a-mole with every spammer who comes along.
Of course, scalable solutions take time to refine, and in some cases there may be collateral damage. There's obviously a "sweet spot" between whacking everything that looks mildly suspicious (thereby causing widespread collateral damage) and letting the inmates run the asylum. Locating and maintaining that sweet spot in a constantly changing Web environment can't be easy--especially when the bad guys are constantly working to protect their own interests.