Google's Matt Cutts released a video on the topic of some of the largest SEO myths out today.
He broke it down into two categories:
(1) Ads and their influence on organic results.
(2) Quick fixes to break Google's algorithm.
On the ads from, Matt Cutts said there are two myths. (1) If you buy ads, your organic rankings will go higher. (2) If you don't buy ads, your rankings will go higher. He also added that people think that Google makes changes to their organic results to drive more people to buy ads. All of this is untrue and a myth according to Matt Cutts.
On the quick fix end, Matt said there is too much "group think" in the forums and black hat forums. He said he sees this all the time where for a couple months one person will say tactic X works awesome, then a few months later, tactic Y and so on. For example, someone might say article directories work, then later guest blogging, then later link wheels and this process goes on and on. Also, someone might say a specific tool works very well. Matt said, the truth is, if someone found a loop hole, they wouldn't sell it as an ebook or software product, they'd use it themselves for as long as possible before others catch on.
Here is the video: