Just think about any relationship for a moment. How long you've known a person is incredibly important. It's not the be-all-end-all, but it is fundamental to trust. If you've known someone for years and years and other people that you know who you already trust can vouch for that person, then you're far more likely to trust them, right? But if you've just met someone, and haven't really vetted them so to speak, how can you possibly trust them?
Companies that employ overly aggressive techniques can get their client websites banned from the search results. In 2005, the Wall Street Journal reported on a company, Traffic Power, which allegedly used high-risk techniques and failed to disclose those risks to its clients. Wired magazine reported that the same company sued blogger and SEO Aaron Wall for writing about the ban. Google's Matt Cutts later confirmed that Google did in fact ban Traffic Power and some of its clients.
Off page SEO: This type of SEO focuses on all of the activity that takes place "off the page" when looking to optimize your website. "What activity not on my own website could affect my ranking?" You might ask. The answer is inbound links, also known as backlinks. The number of publishers that link to you, and the relative "authority" of those publishers, affect how highly you rank for the keywords you care about. By networking with other publishers, writing guest posts on these websites (and linking back to your website), and generating external attention, you can earn the backlinks you need to move your website up on all the right SERPs.