They can easily be clouded by the short-term Adsense profits, which will abate, if they rid their indices of the spam. However, from a long-term perspective, the deluge of spam into their index could (and I think is already to a certain extent) turn people away from their products, namely, the use of their Search Engine.
We´re on the same page here. Google needs to be clear wether they want to support webpages and publishers that provide value added to the surfing community or wether they want to fuel an ever growing gang of thugs that slowly but surely turns their index into a swamp. I fear that the short term reporting pressures of the stock market may force google to take a more short sighted strategy than would otherwise be the case. They also seem to follow this ungodly strategy of wanting to dominate every single segment of the web rather than focusing on their core competency which is their index.