Do you have email addresses of your customers?
Do you have them in twitter?
Do you have them in any platform?
Propaganda is the key to product success.
I guess email address was required to create account, so yes, anyone who traded or made account on Op's exchange is stored in his database.
There is no requirements to use social media, in fact, I almost never follow any kind of service on twitter.
Propaganda is rather negative word - we can better call it "building awareness". And yes, it is required to be successful.