That's just from a quick google. Back in the day there were stories of "A Visit from Mr. Brown" or something like that. The NSA or "some agency" would go around to anyone making crypto or operating systems and ask to be given backdoors in exchange for deals on export restrictions. Periodically a government agency in another country would find them and we'd be embarrassed. These days it's not as common since crypto exports aren't restricted (much) so the threat of, "If you don't add a backdoor we'll label your software a weapon and you can't sell it to the world." doesn't work.

Then again, could all just be a huge conspiracy.....mwhahahaah.