I see it happen all the time - companies using the same coupon they advertise their special deals on HostingDiscussion as they use on WebHostingTalk. I've pointed this out to companies countless times, yet more continue to make this mistake.
So you are either not serious about your marketing or you are just lazy. There can't be any other explanation.
Think about what happens when someone from this community uses the coupon meant to track performance of another resource?
Here is what happens. The credit goes to that channel. Following this result, you increase your advertising presence there, perhaps even invest in a sticky or another advertising position, all the while not knowing the original source of your newfound customer. As a result, your marketing effort and budget is wasted. Even if you only take advantage of free advertising resources, as a business, don't you want to know where you get the most attention and prioritize your time and effort accordingly?