This kind of game, or virtual world since that name hardly does it any justice, is about character creation and evolution. But it\'s also about relationship between characters, and this is the interesting part. Actually, it\'s the only part that really works currently in the case of Planeshift if we put aside the evil crystal hunt.
This evolution and those relationships can be expressed in both the social behaviour - the roleplaying mainly - and the statistics. Up to anyone to choose the amount of either part he or she wants to be spending time on, but having both surely makes the overall experience much more interesting and rich. It gives a set of goals to achieve, constraints and a pleasant environment in which you can proceed to these goals, make other profit from them or help them with theirs, be acknowledged and so on.
One way to illustrate this is the grouping of people into guilds, clans, groups etc. What would be more natural for individuals for characters who have a common ideal than regrouping and working together for this ideal ? As the environment becomes more complex and the competition with other guilds increases, guilds will have more importance. That allows people to work out things together, make better decision and support each other, but also to take advantage of their complementarities, for example in crafting or fighting. In such games it is common to see groups sharing statistics during quests, and it makes sense: it gives an incentive for people to act together and not individually at the expense of others, and it reinforces the feeling of being part of a team. That is also an added difficulty, which helps in term of interest longevity. But I don\'t want to go deeper in this topic, that\'s something which has been discussed in length, over and over again.
However, guilds can be big, counting many people who don\'t necessarily have a lot in common with you except for the guild ideals and beliefs. Among people within or without the guild, you may find a few very good friends though, with who you happen to share the same points of view on many subjects. At some point, you may decide it would be interesting to develop the characters\' relationships further, making them brothers/sisters in arm, parents/child, or of course to marry them.
As in the case of guilds and parties, you could emphasize either the roleplay, the statistics, or both.
The decision of marrying two characters may find its origins in many different motives. I see no reason for denying the fact that some couples actually feel something for each other - they might even know or get to know in real life - and feel the need to symbolise their love within this community. They may also be good or close friends who trust each other well enough, and find it an interesting experience to add more depth to the story of their characters, to symbolise the ideals they have in common, or even to use marriage as a metaphor to prove their faith, and use this bond as a mark of engagement regarding the fate of their characters in the game.
But marriage could also be used for the evolution of the character in itself, like it has been nicely stated before in this thread. Why not use it as an additional way to increase the possibilities and depth to the game ? Conditionally modifying the parameters of the characters sounds like a very good way, if not a necessary one, to go in that direction. \"for richer and for poorer, in sickness and in health, until death do you part\" meaning of course that it shouldn\'t be only for an advantage. Firstly, because the game has to remain fair to the poor lonely characters

, and secondly because it would be more realistic and a (further) good motive to take care of the other character in every situation as it should be.
It could translate into increased strength, will, charisma and so on like said before, when both characters are acting together, or into the alteration of certain skills depending on the relative nature of the two characters in order to favours complementarities, though it may become complex to set up. For example, two mages with opposite Ways like Crystal and Dark would see little advantage of being together (and that should indeed reflect the different and perhaps incompatible beliefs of their owners), unless they are willing to change one way or another. On the other hand, Crystal and Blue together would see their healing and purification powers strengthened. Another easy example is a Healer (Crystal Way) and a Fighter (any weapon skill, or armour).
Then it would have to translate into other modifications of the parameters when the situation tends toward an unsteady situation. To keep the last example, the fighter could have increased strength and agility if the beloved one gets hurt, at the expense of intelligence and armour, as if only a desperate act could now save them both

And of course, in case of death, the grief could be symbolised another way and shared among the couple. Likewise, prolonged absence would have negative effect.
The couple may naturally desire to have children, an existing character would then be adopted and see some of his/her skills modified according to the \'inheritance\' from the parents.
Besides \'simple\' character parameters consideration, marriage may also imply a lot of aside advantages and disadvantages the players could have to deal with. For instance, the economical system could take this into account, if it ever proves to be complex enough, but this is getting too speculative at the moment. The couple could receive a bonus (gifts) when getting together, and suffer a penalty when divorcing etc.
The more possibilities, the more interesting it gets, and in my opinion it is by using every one of them, both in terms of relationship, roleplay and statistics that people can fully appreciate the experience, and stay longer in this project.
Just a few thoughts from another perspective...
