I understand what you mean here opinionista. I think of my last name (my father's name) as a part of my identity because I've always had it all my life. It would be hard to imagine all of a sudden calling myself something else.
The duration of the association with the name seems important. And, also practical things like my degrees are in my current name, etc. I wouldn't be willing to change it really. Not that it matters (since there's no chance of me marrying a man)... but hypothetically speaking.
Well, you could change your name, even if you married a woman. I read that Portia de Rossi is changing her last name to De Generes.
I've been married 30 years. I kept my name when I got married and our two children have my last name. All the things people said would come to pass: confusion, errors, loss of identity, etc. etc. (you should have heard some of the crazy things people said to try to talk my husband and I out of this decision) never happened.
I like being married. I truly believe that if I were me in every way that I am now, except for being a lesbian, I would still want to be married to the woman I love (if that makes sense). Marriage has given my life stability and focus and I think it is an important part of who I am.
L