I cannot understand why people insist on hating Telegram for their choice of tradeoff between convenience and privacy. People who care enough about the subject should know when and whether to use it for their communications. For everyone else, it's an outstanding alternative to Messenger/WhatsApp and Viber.

Edit: I'd also like to add that maybe we need to make a distinction between the notions of privacy and secrecy. Privacy as understood by the majority of people is a broader concept than what more technically inclined people associate with the matter. I believe that then Telegram's decisions and use case can become clearer.