I used to play a ton back in High School and early College and had amassed a very large collection. I think the main reason I stopped was because I've moved away from all of my ol' Magic buddies after college.
The other big reason is because I think I just got overwhelmed. I was a bit obsessed with Magic and bought a lot of cards... tried to keep a pretty massive collection and acquired cards from each new set. But they kept releasing so many cards, so many sets, so many new card types, and a wide variety of zany abilities... it just became too big of a hassle to try and keep up with it. By the time I managed to collect a good amount of cards from one new set and learn their abilities, it seemed like TWO new sets would be released.
Either way, I've always been very passionate about Magic. It's a great game, and even though I don't actively play, I consider myself a pretty big fan. I had jumped into Magic Online a few times... maybe I'll sneak back in there for a little bit and see what I've been missing. And perhaps I can reconnect with some of my old Magic buddies through there.