I think the main reason you see a lot of heroin users and opiate users coming to these forums and not so much crack users is because of the class of people / type of person who use each drug.
In the US there many more cocaine and crack users than there are heroin users, but, (and this is also speaking from personal experience), crack users for the most part tend to be lower class, less educated, more wreckless types. Heroin users for the most part are more educated, middle-upper class types, who also happen to research the drugs they use.
Many crack users dont use the internet at all and are too strung out and busy always trying to score more shit and they dont wanna just sit and relax behind a computer a chill out. Whereas heroin users, once weve gotten our fix, we are perfectly content to do a shot, chill out for 4 - 6 hours and just relax, read the forums, nod out, chat with people, etc. Whereas someone who is using crack, does not have that time to chill out and relax, as soon as they take a hit there thinking about the next hit and how to score it, not how they can chill and enjoy there high.
I have smoked a good amount of crack in my day, but it was never my DOC, heroin has been my DOC since i was 16. I suspect most heroin users here have also used crack, or use crack as well as heroin, but it is not there DOC.