Matt Cutts, the lead at Google's webspam team, recently announced during a panel with Danny Sullivan (recapped at SearchEngineLand) that Google would be working on a penalty for over optimized sites. Anchor text over optimization immediately comes to mind as a starting point or stuffing alt tags, but lets dissect his announcement piece by piece.
I'm pulling three items discussed and the translation that went on in my head.
Quote: "We are trying to make GoogleBot smarter, make our relevance better..."
Translation: We're seeing sites succeed through off topic in content link buys. An example would be a post about pet medications and linking out to car seats because the article talks about not having to set up car seats & packing the whole family into the car when you need to buy pet medications. These types of links are working at the moment and I'm hoping this is Google getting relevance down better so these types of low level link buys won't work.
Issue: Anyone can build these spammy links. You could easily sink a competitor if you spent $5k and drowned them with on topic links in off topic posts. It'll be interesting to see how Google can apply this as a site penalty vs just penalize the sites selling these links.
*Update: On August 8, 2013, Google created a section of webmaster tools to alert sites when a manual action/penalty has been applied to their site. Find out more information about manual actions, typically citing links as the reason, at the Google Manual Actions support page.
Quote: "...looking for those who abuse it, like too many keywords on a page..."
Translation: You know those sites that have a nice homepage, but then you look below the footer and there's 8 paragraphs of keywords stuffed content? Yeah, this applies to those sites. It makes no sense to have a footer with more content below it than above it.
*Update: this continues to hold true through 2014. Sites that utilized giant chunks of content below their footer took a dive and this is considered a poor practice as all of that text isn't useful for users, it's entirely meant to fool Google into crediting more relevance.
Issue: This could be a great addition to an over optimization penalty. The only issue I'm seeing is if it lumps in companies with a long disclosure at the end of every page. The fact that it would be at the end of every page should help Google be able to parse those out.
Quote: "...or exchange way too many links or go well beyond what you normally expect."
Translation: There are a natural amount of reciprocal links for sites. You have customers you link out to & they link back, partners who sell complementary products & links to the BBB that will link back to the site. There is a threshold for reciprocals and they're dialing it down. The reciprocal link radar at Google might go off right now when that percentage of total links is at 25% or 15% or 5% right now, but I'm reading this as Google raising flags at a lower percentage.
Issue: Large client lists that link out could be an issue if you're an email marketing service or provide wp themes. I'm sure there is a better example, but those are the first two that came to mind.
This over optimization penalty could never happen. Google has rolled back other plans after finding that they weren't a fit. The above is total speculation and I could be way off, but digging into SEO day in & day out I wouldn't be surprised to see one of these included into the potential upcoming over optimization penalty.
You can follow me at @adammelson as I'll be updating in our blog if we see any new developments.