Absolutely not. In fact, Google offers many tools that were made specifically for people performing SEO, and they encourage webmasters to optimize their sites for the search engines. However, Google does have an issue with people employing "black hat" SEO techniques. Black hat SEO involves tactics that intentionally trick Google's algorithms, like spamming keywords, using link farms, cloaking content, and other nefarious practices. It's important to only focus on "white hat" SEO tactics that will improve your site and demonstrate value to the search engines; otherwise, you can be removed from the search engines entirely.