We all remember the day Felix Baumgartner supposedly leaped from the edge of space, parachuting down to Earth from a height of 39 km.
Here's a still image from the official, NASA-approved video:

Now, at 39.000 meters, curvature should be clearly visible. In addition to this, the surface blow Baumgartner is clearly quite flat, so discerning the curvature should not be difficult at all. However, in this picture, the curvature of the Earth is obscured by the use of a fish eye lens. How convenient.
However, the fish eye lens which keeps us from seeing the event as it actually unfolded can be removed using Lens Correction tools. I went to the trouble of digitally correcting the image, and now we get...

Ta da! Does this look curved to you? Of course it doesn't. The horizon is flat as a pancake - as it is in real life.
Hopefully this will be enough for some of you see the wool that has been pulled over your eyes. The real world is out there, folks - you just have to look harder to be able to see it.
Source, though probably unnecessary:
http://www.howitworksdaily.com/how-high-do-you-have-to-go-to-see-the-curvature-of-the-earth/