I've never known anyone personally, but I have seen the effects of gambling addiction. Loss of job, house, cars, and more important, family. People who can't control their addiction and get help for it often lose everything.
Like any addiction, it can easily destroy you. I had a massive drug problem when I was younger, but I was lucky enough to beat it. I've now been clean for 18 years, but it's a never ending battle to keep from falling back into it. When you have heavy stress you think things like "A little bit of blow would settle me down". There's no such thing as "a little bit of blow". Do it once and you're back in.
@Rain Dew has said that if I do fall back in she would do what she had to to get me help. But if I refused, or kept using in secret, she would leave me. So I fight myself to keep from going back. I have a medical marijuana card, so that helps if I feel that I absolutely have to get stoned.