Many people wonder why Google hand editing seems random or incomplete, and why some of the best channels get edited while worse stuff is left untouched. Here are some of the reasons Google does a poor job equitably policing the web:

• The web it too large to police and engineer time is expensive.
• Policing certain segments produces unwanted blowback. How often do large corporations or influential bloggers get policed? (It is rare, and when it happens, it is sold as a side effect of feature for users.)
• When issues become popular they get prioritized. Many times Google won't react unless they feel they are forced to. Sometimes they will lie and say they care, and then do nothing. Back in April I highlighted the Netscape search results in Google. Matt Cutts thanked me, but guess what...those Netscape lolita preteen search result pages are STILL ranking in Google, along with a bunch of other search results.
• If they edit in an incomplete or random fashion they evoke fear
• It is easier to control people through fear than to create a perfect algorithm
• They have no need to hand edit the worst offenders. If they are competent programmers the algorithms should take care of those sites. They sometimes edit a leading sites in a field to send a signal. They may throw in a group of other sites if they need to create cover, but their goal is to send a message and alter behavior.

To appreciate how hard it is to police the web read Eli's recent post on how to create an SEO empire. How can Google compete with that?