There are some serious issues with Telegram's cryptography it seems: https://security.stackexchange.com/questions/49782/is-telegr... and http://unhandledexpression.com/2013/12/17/telegram-stand-bac...

See also http://thoughtcrime.org/blog/telegram-crypto-challenge/ (comments: https://news.ycombinator.com/item?id=6936539 )

From the FAQ:

Q: Why not just make all chats ‘secret’?

The idea behind Telegram is to bring something more secure to the masses, who understand nothing about security and want none of it. Being merely secure is not enough to achieve this — you also need to be fast, powerful and user friendly. Telegram is a secure and powerful alternative to mass market messengers and a fast and user-friendly alternative to secure messengers. Hence the two types of chats that we have: ordinary chats and Secret Chats.

The important thing to remember is that all Telegram messages are always securely encrypted. The difference between messages in Secret Chats and ordinary Telegram messages is in the encryption type: client-client in case of Secret Chats, client-server/server-client for ordinary chats. This enables your ordinary Telegram messages to be both secure and available in the cloud so that you can access them from any of your devices — which is very useful at times.

In non-secret chats it even saves all messages on their servers. You can then 'conveniently' retrieve all non-secret your messages when setting up Telegram on other devices.

For non-secret chat it's even worse than Whatsapp, because Whatsapp reasonably convincingly simply relays messages, only storing them on their servers until it is delivered.

Its headquarters are not in the US, so at least the NSA has a slightly harder time getting data access.

No. Not default. 1:1 encryption optional and group end to end encryption not possible.