Transmitted Ahmad. Narrated Mu'adh bin Jabal (r.a.): "Allah's Messnger (s.a.w.) said: 'Verily Satan is the wolf of a man just as the wolf is (the enemy) of a flock. He seizes the solitary sheep going astray from the flock or going aside from the flock. So avoid the branching paths; it is essential for you to remain along with the community.'" (Mishkat [1/184])
The Qur'an and Sunnah of the Prophet (pbuh) warn us against the dangers of bida and internal division (forming sects and denominations). Those who complain that the "gates of ijtihad" need reopening should reconsider their beliefs. To continue the analogy of the hadith, it is better to be alive, even if one is a "herd animal," than dead, being feasted upon by Shaitan.
Wa Allahu 'alim.