[umeshunni]

It self selects for people who are great at talking about themselves i.e narcissists.

[doublekill]

I think the intent behind question 3 is to find people who want to work on something that defines their life enough it makes it on their obituary.

Selecting for life passion, not temporary dreamers.

[detaro]

Bit obvious for that, isn't it? (Although I guess "willing to say whatever they think YC wants to hear" might be part of the filter too, possibly in multiple ways)

[vex]

If you don't have anything interesting to say about yourself or your ambitions, maybe you just aren't that interesting of a person...

[avmich]

But maybe not?