I work for an IT company and recently had to go abroad for attending a business meeting. I applied for a visa and had to send my passport to Delhi for the stamping. Since Blue Dart is the only private courier company in India which is authorised to handle passports, my passport was sent to the embassy through Blue Dart. However, when they delivered the stamped visa, the package was damaged and the passport had a hole in it! Obviously the damage made my passport invalid and my trip had to be cancelled. I had to apply for a fresh passport and paid a fine to the passport office for something that was not my fault.
So, a word of caution to those who are planning to use their service for sending important documents - Don't. Blue Dart is not a responsible company.