Personally, I have never used Telegram. I knew they had open source applications, but since the actual server side architecture was closed source and whatnot, I decided never to touch it.
Discussion
Yes, it’s clearly not the best setup privacy wise but I don’t think it’s ever been the focused of #Telegram (even if some may have perceived Telegram as more private that what it really is). However, it’s an unmatchable tool for the dissemination and access to unfiltered information.