A surprisingly large percentage of people fill out the application form incorrectly. Most of these mistakes we can deal with, but there are two things you really want to get right:
1. In the question asking about the details of each founder (name, age, education etc), one of the things we ask for is an email address. Do please include one. If we want to ask you questions about your application, or invite you for interviews, we need to be able to contact you.
2. In the questions asking for the YC usernames of all the founders, and of those who will come to CA if funded, please make sure that these fields contain nothing but YC usernames (not proper names), and that the second is a subset of the first. It's amazing how often the first field contains fewer names than there are people whose details are supplied later, or (more strangely still) the second field contains a name that is not in the first.
(Edit: I was using commas instead of spaces, which might account for the weird behavior. Does YC search the usernames for each token? Because then only the last names would have had no comma, and so they they would remain)
So, I can't really remember if it was just me, but it's possibly a bug...