Earlier quoted context omitted.
And? It still has key sizes, the enemy still knows the system.
Steganography is solidly a "security through obscurity" thing. Sure, we comp-sci people don't care about that, but spies do. There was that Russian Spy who was transmitting data for years on her Facebook account through steganography pictures on her Facebook account. http://www.technologyreview.com/view/419833/russian-spies-us... The FBI didn't know about it until after she was caught. So believe it or not, Steganogr…
I think one of the reasons stego works is because of the sheer amount of data being generated and shared in the modern world.
It's kind of a blessing and a curse for spy agencies. On the one hand, they love to collect data, and the more the better, since with more data to analyze, they can potentially learn more things. But the more data there is, the more computing power they have to throw at it to make sense of it.
So it's really not surprising that data can be hidden from spy agencies (possibly by relatively primitive means even), because they probably don't have the computing power (vast as their computing power is) to effectively run every possible detection algorithm and all their highly sophisticated (and probably computationally expensive) steganalysis software on so much data.
Videos, since they are so huge compared to other media files like text or audio, have always seemed like an ideal medium for stego to me. Of course, it's more difficult to preserve one's hidden data on sites like youtube that re-compress the videos that get uploaded to them, but any site that hosts original videos unmolested should be ripe for stego.