I have played for a long time, well before multiplayer was out. I was always playing SP then, talking to people on skype who were also playing SP. When multiplayer came out I never really touched SP that much. Still don't. Played for a long while on SMP, had my preferred server. Eventually got a mod spot, then got Admin, which was nice to start with but took the fun out.
I sort of lost the drive there, but then convinced my friend to buy it after I got banned from the server I was Admin on because the owner went insane and banned half the server. Teaching him to play brought back the feeling I had when I first started playing. We server hopped, eventually finding one we liked. Stuck with that, convinced another buddy to get it. Both of them are now addicted to it. I see what I once felt about Minecraft in them and it inspired me to get back into it. We ended up buying our own server and are building it up for an eventual public release. After that two more of our friends bought MC. I feel like sort of the elder, teaching them all of what I know.