Thor is a god, specifically, he's the thunder god, super specifically, he's the Norse god of thunder, storms, and beating the pulp out of things with his magic hammer, Mjolnir (just imagine I did the umlaut on the o). Thor is an unruly god, short on temper and long on power. When he approached, you never knew for sure if you were getting the clenched fist or the open palm (though smart money was on the first), and small business SEO services across the world have come to view Google in pretty much the same way.
The latest victim on Google's mighty hammer are websites that have manipulative link profiles. For those of you who don't know, manipulative links are any links that aren't natural and thus are trying to game, or manipulate, the system. Bought links from a link farm? Spamming forums? Anchor text too spot on? Get ready for the hammer, baby.
A new report from Portent, a marketing agency in sunny Seattle, shows the pattern of Google's Penguin updates and their standard on bad links. Essentially, sites used to be able to have 80% spammy links and still rank. In spring of 2012, that was cut down to 65%. In October, Google began to punish sites that had as low as 50% spammy links. The following graph is from their report:
Remember, these aren't sites that got penalties. These are sites that were analyzed by an algorithm and then plummeted in the rankings. October was the last big change, but now that Penguin is an ongoing part of Google's algorithm, we can assume this number will continue to gradually drop over time. Soon enough, having manipulative spammy links in ANY quantity will draw the ire of Thor and his mighty hammer.
What can you do? Fix your bad links! Get rid of the forum spam, change up your anchor text to make it more organic, use the disavow tool if they aren't under your direct control, but just get rid of them. If you want to chance it and wait until your rankings start to slip before you make a move, that's your prerogative. By all means, wait for the hammer before changing anything. More room at the top for the rest of us. (All superhero pictures belong to Marvel and DC comics, except the bottom one looks like a totally rad crossover that now I have to buy.)