Geni has the option to display a woman’s name as i] her maiden name or ii] her married name.
There are some cases where we do not know the lady’s maiden names and in this case I would name her as Mrs X followed by the husband’s family name or leave the family name blank.
On Geni if the family name is left blank it is linked to hundreds of other one name entries.
There is a fundamental problem with only displaying the husband’s family name.
What if the lady married twice or even more times?
Let us look at one of my ancestors.
Mary Shatswell 1643-1709 who was born and died in Massachusetts.
Mary’s maiden name is Shatswell
In 1662 Mary married William Dale
In 1666 Mary married Nicolas Smith
In 1675 Mary married Charles Rundlett
Those of you who use the married name on Geni can now advise the rest of us which family name you would have Mary listed under.
In my opinion it is always better to display the maiden name (when known) to avoid confusion.
I have been using an alternative description that I like better than Mrs X. I have been using "Unknown, wife of ____" in the first name tab.
I agree that the use of the maiden name is very important, when that individual is not known by a specific name (Eleanore of Aquitaine for example), and actually has a maiden name (not true in early history).
When you look someone up you look for their birth name. You look for Mary Shatswell, born xx/xx/xxxx. You look to see when, where and to whom she was born, then for marriage, etc. Even if you start with who she was married to, in order to find the rest of the family you need her maiden name.
If you look up Mary Rundlett, you may well come up with several because Mary is such a common name but they'd be from the other side of the family, so to speak. True, there's probably more than one Mary Shatswell but not in one individual family (parent/child group) usually.
If a woman's maiden name is not known it make sense to put her married name, possibly with a note - Mary Rundlett (X) to the effect that maiden name is unknown.