On Indian last names...
Having lived in quite a few different regions of the country and having studied at an institution where I met people from every state in India, I have had the opportunity to synthesize the variety in Indian last names. I categorize them as below (Please note, this does NOT cover last names of all religions):
1. Use of father's name as the last name - Several South Indians, predominantly Tamilians seem to take this approach. For example, Arun Rajan, Sulu Gopal, Kartik Ramakrishnan, etc.
2. Use of caste / community as the last name - Examples are abound: Satish Iyer, Utpal Patel, Laloo Yadav, etc.
3. Use of the ancestral village/place of origin as the last name - Harish Mysore, Vikram Akkineni, Sanjay Manjrekar (Manjre arguably being the name of the village that this person's ancestors hail from), etc
4. Use of 'Gothram' as the last name - Arjun Bharadwaj, Arun Kashyap, Mita Vashisht, etc.
5. Use of ancestral profession as the last name - Feroz Contractor, Nilesh Batliwala, etc.
There, hope that adds some clarity to the profusion in variety of Indian last names. Feel free to let me know if I missed out any! :)
Some other observations -
1. Christians in the South sometimes have Hindu first names and Christian last names (Harsha Mathew, for example)
2. To further throw a wrench in the works, some south indians use the name of the village and the caste/father's name in their full name: Hardanahalli Doddegowda Devegowda, Gadicherla Venugopal Rao, etc.
3. In Bengal, Bhattacharjee and Bhattacharya both mean the same thing, although they are 'different'.
So, tell me - Which category does your last name fit into?