A very helpful list from this article:
Khalil, Mohammad Hassan and Mucahit Bilici. ‘Conversion out of Islam: A Study of Conversion Narratives of Former Muslims’ in Muslim World, Vol. 97, Jan. 2007.
Intellectual/Ideological Motivations
1. The status of women in Islam.
2. The contradiction between Shari‘a and human rights.
3. The problematic nature of the Qur’an.
4. The character of the Prophet and other Muslim leaders.
5. Islam as illogical and unscientific (e.g. vis-à-vis the theory of evolution).
6. The eternal damnation of good non-Muslims.
7. The unnecessary, strict rules and expectations of Islam.
8. Islam as not universal, but rather Arab-centric.
9. The dubious historicity of the Qur’an and Hadith.
Social/Experiential Motivations
1. Encounters with bad, cruel Muslims.
2. Muslims as oppressive.
3. Muslims as backward.
4. Muslim ill-treatment of women.
5. Muslim ill-treatment of non-Muslims.
6. Muslims in a state of illusion regarding their own religion.
