Many of you here in the UK would ask, what on earth is a "Growth Hacker", let is start start by quickly having a quick look at a brief description of this term. "Growth hacking is a marketing technique developed by technology startups which uses creativity, analytical thinking, and social metrics to sell products and gain exposure. It can be seen as part of the online marketing ecosystem, as in many cases growth hackers are using techniques such as search engine optimization, website analytics, content marketing and A/B testing. Growth hackers focus on low-cost and innovative alternatives to traditional marketing, e.g. utilizing social media and viral marketing instead of buying advertising through more traditional media such as radio, newspaper, and television".
Growth hacking has been particularly important for startups in the USA, as it has allowed for a "lean" launch that focuses on "growth first, budgets second." Facebook, Twitter, LinkedIn, AirBnB and Dropbox are all companies that use growth hacking techniques at start up.
The extensive use of "Big Data", analytics, social media and high impact graphics characterise this particular marketing technique, whilst the term Growth Hacker not widely used here in the UK, I am sure as more online marketeers here in the UK see the benefit of promoting themselves in this manner, that we will see more Growth Hackers springing up and will see the term used more often.
The reality is that many agile seo and marketing agencies have the knowledge and skill set to do the same task.