It's a big deal because it seems like a lot of trouble for someone to...
a) make fake satelittes that don't really orbit the Earth
b) make fake space programs that somehow don't go into space
c) start wars (so I've heard) to protect the secret
d) fake satelitte radio, TV, and Internet
e) create fake photos and videos from space and other planets
f) brainwash everyone so when they look through their telescopes the other planets are round and the moon is round
g) fake GPS technology
h) brainwash anyone who's ever been to the North or South Pole
i) keep all the scientists and astronomers, millions worldwide, from telling everyone the truth
j) comprise thousands of photos from helicopters
k) brainwash everyone so that when you look across the ocean from high up they can't see a minute curve
l) trick the creator of the movie 'Spin' or create it themselves
m) organize a global secret-keeping pact without a single leak
n) manufacture millions of globes for centuries
o) fake day and night and the rise and set of the Sun
p) fake rocks brought back from the moon
q) fake global warming and the ozone layer and atmosphere
r) trick people into thinking they can fly and sail around the world
s) prevent anyone on Earth from seeing the edge of the planet and destroying every single historical record from the history of humanity of this happening
t) invent ideas such as "physics" and "gravity" for the conspiracy
u) create some sort of massive machine that changes the entire physicality of the planet so that objects thrown West with the same force as object thrown East will go farther (because of the Earth's rotation)
v) make sure thousands of people who sail chips and fly planes never see the edge of the Earth or at least make them never talk about it
w) blockevery single media outlet (except this and one other website) and indepent scientific study on the planet that says that the Earth is flat
x) fake the return of every single spacecraft to Earth
y) fake the deaths of the astronauts who have died
z) fake historical records of anyone who has sailed or flown around the world
a-1) fake pictures of the Sun and estimates for its distance from Earth and fake its size, heat, and make-up
a-2) inventing modern meterology and every single weather forcast with satelitte images
a-3) fake every map of the world and find no disputes from anyone in the world
a-4) fool all military into believing long range weapons can account for the curve of the Earth
a-5) fake our models and understanding of the solar system
a-6) fake NASA and everything they have accomplished (like this for example:
http://www.nasa.gov/centers/goddard/news/topstory/2003/0206mapresults.html)
a-7) invent
everything that has to do with the origin of the Earth (all of this information for example:
http://www.pbs.org/wgbh/nova/transcripts/3111_origins.html)
a-8) fake the effects of pendulum experiments that prove the Earth is turning (I have seen one of these working myself)
a-9) force into silence, trick, or brainwash the few tourists have gone into space
a-10) fake the study of how birds fly
a-11) massively falsely educate everyone
a-12) fake or brainwash everyone into seeing the slightly curved effect of the sky and clouds when the clouds are light is right
a-13) fake the way we look at stars especially from different spots on the globe, with the naked eye and our own telescopes (different positions on the globe, different angles, different stars)
a-14) make sure thousands of scientists and astronomers lie to their families every day
a-15) fake the rockets that go around the world (such as the one filled with cremated remains)
a-16) fake hot air balloon flights
a-17) fake asteroid impacts and predicted asteroid impacts
a-18) fake everything we know and practice about the Sun's rays such as UV protection
a-19) fake eclipses and solstices and equanoxes (and all this information
http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html)
...without any imaginable reason. I am still trying to think of why exactly the world's governments would do this, pretending it is possible.