Write a brief on why you fit current role ?

This question seems relevant during an interview but I have interviewed with a company which wanted me to write a sample of product document I would produce if I were hired (they gave me a scenario) and why i would be perfect for this job before they take me to the 3rd round of interview.

Intially I thought this was only relevant to the specific job I interviewed for however one of my friends was just contacted by a web company and they wanted him to write why he is a good fit for the role.

This sounds surprising initially but then it does make sense. First such request would be for jobs like Proposal Manager, Product Manager etc. Where one of the expectations of the job is to write business requirements, documents etc. Second it helps the candidate himself to clarify his position (i believe if you write it down it becomes clearer) and you think deeper on why you think this role is a good fit and why you want to take it. Third you can add some points to your interview process by writing a solid "why I".

So if you are targeting jobs where it is expected out of you to write proposals, requirements documents etc. be prepared for such requests from potential employers.

Also one of the favorite questions of interviewers is "why should we hire you?" You cannot ignore to have good answer for this question.