well - for one 1. You (the founder of a startup in India) would have a better understanding of the Indian technology consumer market and the application of your idea to the Indian scenario than a tech company which is originated elsewhere. 2. You are in the same time-zone as 1 billion other people. If you have ways or means of crowd-sourcing any tasks needed for your startup - where better to crowd-source than here (of course this depends on how effective are you at crowd-sourcing) 3. If you can spot an opportunity in a crisis - then this place offers you the ideal basecamp to look for those crisis/opportunities.

I could go on.

I guess at the end of the day it all depends on the problem you are looking to solve or the "big idea". For e.g. If your startup is about making it easier for suburban residents to interact with their neighbors or promote neighborhood activities - Mumbai would be the wrong place to start that startup. But if you are looking at implementing infrastructure technologies for dense urban setups than Napa Valley, CA wouldn't be ideal.