domain Yell.hk

not sure what you are going for, the Chinese people are a quiet people so its not social media. Shopping is huge in hongkong (.hk) so a mall site would be excellent. Either way its a 3L.hk and a reseller would pay you high xx or low xxx. Seek enduser.

Isn't this a good domain name for local yellow pages considering the following websites?

British yellow pages Yell.com
Russian yellow pages Yell.ru
Yellow pages Yell.net
Biz web Yell.us
A brand Yell.de
Japanese Yell.cc

not to mention many websites containing "Yell"

there you go, you answered it yourself. You needed encouragement. lol.