Yeah, I have seem many hit the skids in various escapades. There are a million sad stories for people that make good amounts of money playing poker. I knew Pros that had to quit because they could not handle the huge sportsbook losses they were taking (what would make someone bet 30K on a Monday Night Game?). I knew Pros that were hooked on games like California Pai Gow and Pan 9 that attract huge gambling addicts. Everyone hears the stories about Pros who go crazy on craps (ala T. J. Cloutier).
I guess a lot of poker players are just gambling addicts. Two instances that always stick in my head, is when a well known poker player at a tournament series in Las Vegas just cashed for 30K, gambled all night long, then showed up for the next days tournament completely broke and needing to scrounge up money to play a $500 event. A few days later, he made a another 5 digit payday, and I overheard him asking one of his close friends to please take the money for him, and to promise not to give him any money for gambling (that was not a direct tourny entry) no matter what he might say, beg, plead, demand, etc.
The other instance was this guy who always was begging for money at any event you went to, whether it was a small $10 entry or $300, etc. If he wasn't looking for tournament entries, he was looking for you to buy him a breakfast. It seems he was broke and struggling forever. Then boom, out of the blue he hit a 40K windfall after taking 1st Place at a Las Vegas MTT, and so many players at the time were so happy for this sad sack. Of course he had a long line of people looking for some payback, but walked out of the casino with a ton of cash. He immediately went out partying and gambling with friends, and by the time the night was over, the guy had lost every penny of the money. Eventually, this guy went back wherever home was in the midwest and took a regular job.