Many people have chosen IIM Bangalore over IIM Ahmedabad. Everyone says IIM Ahmedabad has a better brand and a larger alumni network, but neither factor is particularly appealing to those who are considering leaving.
Many undergrads, particularly those with offers from consulting firms, investment banks, or private equity firms, choose their current job over an MBA at IIM A/B/C. After earning an MBA from a foreign university, these men can use their experience to land better jobs.
Like every other institute, IIM Ahmedabad has also seen people declining admission offer. Although it is not very prominent, we can’t say it's negligible. My friend is an alumnus of IIM Ahmedabad and he knows a couple of people who did this.
While the above examples were of people who didn’t join IIM Ahmedabad, there are cases of people not joining IIMB/IIMC. One of my batch-mates from IIT Kanpur didn’t get into IIMA but got into IIMB and IIMC. Later, he decided not to for MBA and instead started working in Mumbai.
This is a clear indication that sometimes it is good to go off the way. It is not necessary to go with mob mentality always. You should follow your heart when you know what’s right for you!