Is it me or are there way too many characters that don't have the same last name as their parent or child. Sometimes it makes sense like when John Locke's dad's last name is different as well as Claire Littleton's dad's last name. Locke's dad constantly changed his name and his last name came from his mother anyway. Claire's last name also came from her mother because her father already had another family.
Sometimes there is a difference in last names that is ambiguous whether or not there is a good reason. Ethan Rom's parents are Horace Goodspeed and Amy. Amy is never referred to by her last name so it could be Rom. It could've been her previous husband's name or her maiden name.
But sometimes there doesn't seem to be any rhyme or reason to why there is a difference in last names other than to hide a character's true parentage from the audience. Miles Straum's dad had many names. Most of them were fake names but not a single one was Straum. I also truly doubt that Straum was his mother's maiden name. I suppose there is a slight chance that she could've changed their names after leaving the island in order to hide from either his dad or the Dharma Initiative but to me there didn't really seem to be any reason to hide from anybody.
Perhaps the worst case of a character's last name being different from his/her parent's for no apparent reason is Daniel Fadaday. We know that his parents are Charles Widmore and Eloise Hawking. The only in-universe reason I can see to hide his parentage is so that Daniel, Penny, or anybody else would not be aware of Charles having children by two different women. But that doesn't explain why his last name should be different from his mother's. It was no secret that Eloise was Dan's mother. There is no reason for their last names to be different. As much as I love the writing on Lost, that kinda bugs me.