When I joined my regiment in 2012, DarthKiller joined the same day, half an hour later. Now - 7 years later - we are both leaders of the regiment, met several times in RL (even with other community/regimental members) and are very close friends.
I met an incredible amount of people in this game, some of them staying in my regiment for several years now. We had huge real life camping trips with more than 60 people in different federal states, went to different amusement parks together, celebrated new year's eve, met with a dozen friends in some of the cities where our players live (Vienna or Frankfurt for example). Sometimes this happened in smaller groups, sometimes the whole regiment or even more than that took part in it.
Pretty awesome ride so far.