Hi, great question! got my brain working over here!
FYI, I'm a growth hacker so I'll try to actually be of use to you here.

First thing that comes to mind is that you might be going about this wrong. Is common for most of us to have a biased researched online to solve a problem we are having, our search is biased because of something we might have heard of in the past so we start with that. When we find the answers we were looking for regarding that biased search we stick to that and get stuck trying to figure out how it applies to us and make it work. In business this is very very common, that’s why a lot of us are here, and a lot of startups need to pivot once they realize that they got pulled into thinking their prior focus what the right one.

You start off asking how to engage more consumers, then quickly moved to a specific strategy that worked for other companies. The truth is that for these companies these tactics were only 1 thing from a variety of efforts. Which is why I think you might be focusing on the wrong one.

Giving away freebies works, but that’s just traditional marketing coupled with their growth hacking techniques. It doesn't work for you, fine.
The reason why your consumers are not sharing as much as they are, or raving to their friends is because they are simply users – what you need is hardcore aficionados in something that you provide.
How? Improve your business development and marketing by super targeting your demographic. Find a subset of your clients who are hard core about what they buy, possibly hard core about international purchases, or a large group who buys the most popular item through your site.
How? Build a persona. You have probably heard this, but is extremely important. {I have continued my response to you through my blog, due to length... please continue reading here: http://UnthinkEverything.blogspot.com }

I have some examples and stuff I hope you enjoy and find useful.