Question: What is the ruling regarding the pilgrims making Khulafaa. as a group (in chorus), whereby one of them makes the talbiyyah and the rest follow him?

Response:
This is not permissible for the non-existence of any evidence from the Prophet (sal-Allaahu `alayhe wa sallam) and nor from any of the Rightly Guided Khulafaa. (Abu Bakr, 'Umar, Uthmaan and 'Alee (radhi-yallaahu 'anhum)). Rather, it is an innovation.

And with Allaah lies all success and may Allaah send prayers and salutations upon our Prophet (sal-Allaahu `alayhe wa sallam) and his family and his companions.

The Permanent Committee for Islaamic Research and Fataawa
al-Bid'u wal-Muhdathaat wa maa laa Asla lahu - Page 394;
Fataawa al-Lajnah ad-Daa.imah lil-Buhooth al-'Ilmiyyah wal-Iftaa. - Question 4, Fatwa No. 5609

Taken from fatwa-online.com