The reason "nobody knows" about the danger is simple - there IS no danger. Those that claim there is some sort of doom approaching is just blowing smoke. Whether for some sort of profit, notoriety, or simply being a "Drama Queen". They crave attention.
I believe is the crux of a lot of the hoopla - some people feel the need to "be special" in that they have a "revelation" or have "secret knowledge of the Ancients", or whatever. Some want the attention, but unfortunately many have no real interest (or knowledge) other than making a buck: "And YOU TOO can receive these 'forbidden/supressed secrets'! YOU TOO can be among The Elect! But only if you order my informative and enlightening DVD! And if you order RIGHT NOW, you can receive my newest book on 'How to Survive'…"
As long as there is anything new or as-yet not fully investigated/studied, there are those who will exploit the uninformed or gullible into thinking "they have the answers". Perhaps "gullible" is too harsh - try "easily pursuaded". When Halley's Comet made its appearance in 1910, it was predicted the earth would pass through its tail, and thousands of panicked people bought gas masks to prevent being asphyxiated by "cyanogen gas". When I was in Jr. High in California (April,1969), several psychics predicted a massive earthquake/tsunami - I saw kids with life jackets in their lockers, or didn't go to school that day. In 1982, the "Jupiter Effect" was supposed to rip the earth apart - and that WAS an ACTUAL planetary alignment! (there IS NO "alignment" happening 12/21/2012, by the way)
"THE OLDEST and strongest emotion of mankind is fear, and the oldest and strongest kind of fear is fear of the unknown." - H.P Lovecraft.
Learn facts, NOT hype. Knowledge destroys "the unknown".