People think this, but it is still highly effective.
Say you want your adversaries to use pencils instead of pens to write their secret notes. You publish information on the risks of pens and how they leak information on an obscure corner of the internet and seed it to a small forum or two. That gets picked up by a government worker in Germany and they put it into their recommendations. That document then gets stolen by the Chinese. Both of these get shared with Iran. The materials are then leaked and you have the Snowden's of the world shouting from the rooftops the importance of using pencils.
While I see what you mean, I can't think of any example right away that are touted by people like Snowden - I see there were many honeypots on crypto, TOR and "encrypted" phones, but other than maybe VPNs I wouldn't know what was shared this way.