The founder (Durov) is a Russian in exile, fighting Putin's attempts to control the encryption keys. Secret chats are not affected, but cloud chats would be. Durov has stated he would rather see Telegram banned in Russia than give in, but the world will know in 2 weeks.
He's not "in exile", it was bluff/PR piece. He regularly visits St-Petersburg, and the main development office was also in St-Petersburg as of a year back right next door to the Vkontakte one.
Durov is a very shady person, I wouldn't trust him with anything that you may want to keep private. Check out how a story by ex-employee of his [1], it gives a lot of backstage info.