I've seen friends get married in world, seen them quietly (and not so quietly) join each others profiles, and I've seen them stay together in a firm relationship without partnering at all. Partnering can mean to some the equivalent to marriage, even if they are also married in RL. It can mean a promise, to keep and love. It can simply be a reflection of whom one are attached to and are happy about it, a way of declaring the person whom one spends time with one's partner. Shouting out to the world in effect that you want this person to be known as a part of your life.
A grand example of the first are two good friends of mine, Marissa Goodliffe and Lachlan Campbell. He is married in RL. They are happily married/partnered in SL and have a strong commitment to one another. They are beautiful together. I have only seen the strong points of their relationship and the outside point of view. However, it is an intimate relationship that they pour their hearts into. An agreement to love and honor in Second Life.
The alternative, of course, is having that love in SL and RL. Difficult to do if married, as it starts to peer closely at the line of adultery. If one is single, however, it depends on your desire to share your RL. How much do you want people to know about your RL, how much of it do you want another person to invade? For some, even single, they still keep things separate. Living a full SL in addition to their RL.
I can understand this concept on some level, but cannot fully comprehend it. Why? Because I am emotional and feel very deeply. I give all of myself and in doing so there is a part of me in RL that gets invested into my SL relationships. Thus the need to discuss upfront the thoughts and desires of the person that you connect with.
My ideal of partnership is simple....it is a connection to a person that I care about deeply, that I want to show visibly to the world around me (in SL) that I care about this person and that I have made a promise to him. Love is part of that picture. For me, it has to be, it means that my heart is in that person's hands. And again, these feelings will carry over into RL.
So you see the complexities of partnering....what are your thoughts?