The mainstream does not care if your cryptography actually works
This is because the mainstream does not care if your cryptography really works. You must only make them comfortable believing it.
Following the WhatsApp acquisition deal, Swiss mobile messenger Threema [1][2] got 200,000 new users within 24 hours [3], each paying at least USD 2,20 for the app in advance.
Threema is proprietary. There is no information as to the protocols and algorithms used. But the public is fine with that.
Not only are users celebrating the app. They feel that convincing their friends to go there is the expression of a new movement, reinforced by the NSA revelations and the WhatsApp deal.
Threema got free press coverage by the most popular and trustworthy newspapers in Germany, including zeit.de, spiegel.de, focus.de, heise.de, stern.de, focus.de, handelsblatt.com and bild.de.
We had that already: Telegram, whose team "consists of six ACM champions, half of them Ph.Ds in math" [4]. Telegram decided to provide open APIs and even start a contest to inspect their cryptography.
As it turns out, this was a mistake: While Telegram has been massively criticized for its contest and rolling their own cryptography [5], closed-source Threema is winning.
After all, people just want to feel save.
[1] https://play.google.com/store/apps/details?id=ch.threema.app [2] https://itunes.apple.com/de/app/threema/id578665578?mt=8 [3] http://bit.ly/1nVb8Y5 (Google Translate) [4] https://news.ycombinator.com/item?id=6916860 [5] http://www.cryptofails.com/post/70546720222/telegrams-cryptanalysis-contest