In EverQuest, such player bonding has become as common as orcs or goblins. The game forces players to interact with others in order to beat opponents and advance to higher levels.
Monsters are too tough to tackle any other way.
Most often, these associations happen on the fly, when gamers group for an hour or two to overcome a particular challenge. It can lead to intimate moments. Tagyerd coos to his female fellow adventurer during a Monday night session. I was partying with this woman and another guy for about a week. And I was subtly hitting on her, being all flirty, chatting privately.