My vice is the Internet, if vice is something that takes one away from healthier alternatives.
I started when training at a training company. I couldn't help myself. It was just so easy to access.
i had always loved writing to other people and exchanging ideas with people outside of my social circle. I didn't travel that much so didn't encounter other geeks like me.
The Internet is my vice. I have no doubt I spend too long on it but I find it such a source of interest for my brain. I love learning as well as interacting with people who see things differently to me. I still live in the village I grew up in and my family live within doors of me; this makes for a great support network but isn't conducive to moving outside one's comfort zone.
My time on the net allows me to learn new stuff every day, to delve deeper into new things I might come across (I love researching things), to interact with people who have similar interests to me, to rediscover things that had meant a lot once but had faded out of my life.
I use a tablet PC these days and it enables me to be in the room with my wife and enjoy conversations but still be able to dip in and out of the net when she is otherwise occupied, say watching television. I am conscious of the need for social interaction in relationships so make an effort to be a part of conversations, see friends, etc. but I still get a special buzz from all that knowledge out there I can tap into within a few clicks.