In my book I discuss whether, and how, a candidate should adopt a nickname when applying for jobs. Another reason, not mentioned in the book, may be that if there’s something in your background you don’t want others to know from the start.
Here’s an example: a while ago a candidate came to my group. A coworker, out of curiosity, looked him up on the web, and, to his amazement, found an old article linking the candidate to an arrest a few years ago when the candidate was in grad school. Obviously, that made us a little uncomfortable around the candidate throughout the day.
Some career websites claim most hiring managers use web tools to do background search on candidates. I don’t know if that’s true on Wall Street, where everybody is so busy. However, law requires a thorough background check before a person can be hired, so your background will be looked into after you pass the rounds and prior to receiving an offer. (More checks will be conducted before you are officially hired.) But if you have something in your past you don’t want people to know — e.g., things that have been sealed or expunged from your records but might still be around somewhere on the web — this is a good time to adopt a nickname, and use the nickname on your resume and in your correspondence. Of course, when you fill out the employment application later, you should (as you must) give out your real name, but nobody says you need to tell an interivewer everything about your past during interviews. Let’s the HR people and company lawyers decide if that "something" in your background is serious. Your job search strategy should be to focus on letting people about your quant skills and doing well on interviews.