Everyone knows you shouldn't have a spammy site, but just what the heck does "spammy" even mean? We know Google doesn't like it, but it's not as though the word has a hard and fast definition (at least not one pertaining to SEO). Google realizes this, and they have recently put up a new page that illustrates business SEO websites that they have flagged as "spam" so that you have a metric when building your own site.
The page illustrates how they identify spam, the types of spam, and how they take action against it. Most of the work is done by a combination of the Google algorithms and physical, personal review. Obviously the personelle time is limited, but the algoritm time is not. This is the problem that many spammers are having. They used to be able to get away with it by flying under the radar, a sort of "they can't catch us all!" mentality. Now, the algorithm has grown so sophisticated that Google CAN catch them all, or at least enough of them to dissuade the rest.
So do yourself a favor and check out Google's examples of spam, but don't let them scare you away from SEO in its entirety. There is still plenty of room for honest SEO done with a white hat on. Look at what Google penalizes, and make sure your site isn't guilty of any of the same violations. If you're unsure, you can always contact us and we'll gladly give your site a quick free evaluation for best practices.