There have been rumors from "birthers" (which you can search the Internet for if you're interested) about the many ways Obama has supposedly "lied" to get into office, one of which is on his bar application in Illinois when they asked about other names you've been known by; what they were actually looking for (and Obama might have very well asked to be sure about, as I've suggested to TSs who've been asked a similar question before) are names that you've practiced law under (to keep disbarred lawyers who've had troubles from sneaking back into practice). In Obama's case, his name was apparently changed to his step-father's last name but changed back to his birth name when he became an adult. Further proof of that is that under the lawyer profiles they have on there, they have a "Former Names" section, but there are many cases of female lawyers who changed their names when they married but didn't start practicing until after that, and in their case their maiden names do not show up (for the same reason that "Barry Soetoro" or any of the other names Obama has been rumored to have used don't show up); the only "former names" that appear are those that they've previously practiced law under.

Obviously Obama is not a TS, but his story further proves a point I've been mentioning on here - when a job application or something similar asks if you've been known by another name they're usually not interested in every name or nickname you've used or been called since the day you were born, but rather other names that records they may want to check are under (and you can ask before filling out the form if you want to be sure). Unfortunately, except for the handful of TSs who changed their names like Obama did either before or right after coming of age (which is who I've been speaking most of my advice to), most in the community will have records that an employer is interested in checking under their original name (and omitting them if asked is a case that amounts to materially lying and will likely have consequences, especially in negative cases like a job you were legally fired from or criminal convictions).