I have friends who do that.  They call me on ICQ and ask if I want to play Unreal Tournament.  I play for a couple hours and than it\'s like 2:00 AM and I send a message that I\'m off to bed.  I get up to go to the washroom and decide to check if there still playing.  Sure enough it\'s 7:00AM and there still playing!  These guys work where I do, and they miss alot of work days, or come in sleepy and cranky from playing all night.  I couldn\'t do that.  
Videogames are an addiction.  I had a friend who stole money from his dad to buy games and he was laid off!  When his dad found out that he was using his bank card and took out $600 total over several months, he smashed his PS1.  His Parents sent him to see a Psychiatrist to get help for his addiction.  He has a Dreamcast, and a PS2 but he plays in moderation and he\'s o.k after getting help.  I think most people don\'t fall in this category of major addiction but it\'s scary to think it happens.