Every industry has it's well known people('notable person'), who are respected. Their word is taken as truth, and getting compliments/advice from them is huge honor for intermediate and beginners. They also get massive social status when entering a site, users will go the extra mile to answer there questions etc. As a result there is huge incentive for users to pretend to be those people.

If a person claiming to be a 'notable person' appears on your site, is it necessary to confirm that they are who they claim to be?

Part 2:

Lets assume that their identity needs to be confirmed. How do you go about confirming them without being intrusive, demanding or offensive?