Spam is the biggest threat to organic search engines, whose goal is to provide quality search results for keywords or phrases entered by their users. Google's PageRank algorithm update ("BigDaddy") in February 2006—the final stage of Google's major update ("Jagger") that began in mid-summer 2005—specifically targeted spamdexing with great success. This update thus enabled Google to remove a large amount of mostly computer-generated duplicate content from its index.
You’ll want to capture users’ emails regularly, both when they purchase…and even before they become a customer. You can use lead magnets or discounts to incentivize email sign-ups and using an email management service like MailChimp allows you to create triggered autoresponders that will automatically send out pre-made welcome email campaigns when they subscribe.