It is an unfortunate fact of life that some people are willing to break the law and hack websites to make some money. Google generally does a decent job of mostly keeping this under control. Recently I came across a good mainstream term that was spammed so bad it reminded me of some super spammed adult serps.
How did this hacker take more than half of the first page of results? The hacker didn't just drop some outbound links on the page. The hacker dynamically inserted large amounts of text that was themed to their outbound links. The hacker also rewrote all internal anchor text to make them themed as well. They basically re-themed the entire website. After they re-themed one site, they then re-themed several other hacked sites and formed a pretty nice interlaced network.
I find it interesting to see a really smart hacker at work. This time I found it more interesting to follow Google's response to this hacker. For some reason Google has not removed these sites from the serps. They are not even flagged as compromised sites unless you do a site: search.
I am not 100% sure what is going on since I do not own these sites nor am I the hacker but it has made me sit up and pay closer attention to Google's response to these originally unrelated (now perfectly themed) hacked sites that are ranking for a fairly competitive mainstream serp.
ps Please keep your Google editorializing to yourself. It does not add to the conversation or help us better understand the different ways Google may address hacked sites.