https://www.geni.com/account_settings/name_preferences
Customize how names are displayed on Geni. These preferences apply to family trees, lists and the rest of Geni. Profiles always display the full name or display name. You may also change these settings in your tree, under the Preferences tab.
David -- Geni has fields for both Birth Surname, and Last Name -- and they are supposed to be used correctly, ie with Last Name being the Last Surname the Person used / went by - NOT the Birth Surname if the person was a married woman who used her husband's last name.
As Erica explains, you can control how you see the name - so you can see it as you think it should be, I can see it as I think it should be - unless someone has hard-typed a name in the Display Name Field.
Hard typing into the display name is to be avoided. For American women, names followed the English Common Law until 1976, when social security ruled that a woman’s “legal” surname after marriage was not necessarily her last husband’s last surname. (I’m over simplifying of course).
As a Geni volunteer curator I am always looking for tree errors by checking relationships - even very distant ones. If I see a “hard typed” display name for an American woman I now don’t know if that profile is likely correct or not at a glance. So I really hope everyone understands that it’s very simple to set your own profile preferences to see Birth surname only, and it makes it more difficult for the World Family tree to hard code.