White Line Fever wrote: ....
If you have a mental illness (fragile mindset) 
...
Unfortunately, many people become obsessive when they become depressed and get locked in rather like poker machine addicts do.
By then it is past the point where they can opt out.
Basic limits of civility need to be required on such sites, and if you are going to run one you need to be responsible for setting and policing those limits.
You are not going to be able to persuade people to avoid these sites if everyone they know uses them, no matter how rational a choice it would be.
In any case it is a bit like saying, "If you fear being bashed by some random drunk don't go near pubs and clubs."