My husbands cousin also didn't change her surname when they got married and she agreed with her husband that if they had daughters they would take the mums surname and if they had sons they would take the dads. However, I think it would be strange for a brother and sister with the same parents to have different surnames. They had two girls which made things easier.
Good luck.
Wow, that's interesting. In some countries, you're not allowed to do this. I'm in Australia, and when a couple has their first child, they can decide which last name to use, but any subsequent children (having the same parents - that doesn't apply if the parents split up and have kids with other partners) will have the same name. I think that makes sense, it would be weird for siblings with the same parents not to have the same name...
Now to answer the initial question: for me, there was no question, baby will have my partner's last name. I was even surprised when my partner asked me if I would be ok to give baby his last name, as for me it wasn't something I even considered not doing.
My parents were married when I was born but then divorced. My mom took her maiden name back, so I grew up with my dad's last name, but living with my mom. That was never an issue for me at all. I actually think it's a good thing, because even if I didn't live with my dad, at least we still had that connection.
And as a previous poster said, I think it's important for the partner to have at least that. I mean, the whole process of pregnancy is foreign to them, they can't do much but just wait for baby to be ready. Then when baby's here, usually the mom is the primary carer (especially if breastfeeding, and because she usually has a longer time at home with baby before returning to work). With all that, the dad can feel left out a bit. Giving his last name is probably something that shows he matters, that he's part of it all and not just a spectator.
We're the ones giving birth, I think it's fair to let the dad give their name...