I've been reading Matt Cutts for over a year. If you read him, you think Google has strong defenses against vendors who game their rankings. On the other hand, some searches persistently produce large numbers of garbage results. This doesn't add up.
That's why I believe this post is credible (read the entire post for the full context):
... I was one of those people who looked down on buying links for a long time. It just seemed wrong – and surely the brain trust at Google would clamp down at some point. I just couldn’t believe that buying your way to the top of the organic results could A) be SO easy, or B) yield sustainable results. That was three years ago.
This scheme of embedding links in free stat counters in order to juice link pop has been around for at least that long – and should be among the easiest for Google to detect. It should be a big yellow flag when a site gets lots of inbound links from totally unrelated sites over a short time period. And it should be really easy to detect the code pattern like the one shown above for those inbound links (it even says “invisible" for God’s sake!). Finally, it is pretty irregular to have a UK page show up at the top of the results for a competitive term like this on Google.com. It seems like that might have thrown a flag somewhere along the line as well. The patterns are easy to spot. But Google is either oblivious to all of these issues or they’ve decided not to do anything about it. I’m not sure which is worse...
Google's defenses aren't working. I know they're having problems delivering almost across the board (Gmail still works well at least!) but this has got to be their number one problem.