I think the experts are saying more like once Every year.
Consider the size of the Earth, the area of Oceans, the area of land, the area of land inhabited by humans with cameras, and you will find the chance
of Humans actually seeing these events are quite low.
Just imagine the amount that fall in the Oceans!!!
I have seen 2 almost as impressive as this, in the past 15 years. The first One I think was space junk, but a huge fireball, the size of the Moon with
a fire trail, that was about 15 seconds long (and slowish).
The second at 9.00pm, watching a commercial jet plane travelling north, when all of a sudden the sky lit up with a huge Arch Light type light (that
bright purpley whitish blue light) and this object fell, what seemed from my perspective, not far in front of the plane...in reality it could have
been 100's of miles away in the upper atmosphere. Only lasted a few seconds. Im sure the Pilots had a change of pants in order. Of course no mention
of this in the media, but I would think the pilot would have made some sort of report.
As an aside, researches in a remote Australian area have discovered an "Extinction Level" impact zone that is now the Worlds third largest. The
strike has left a crater 200km (120miles) in diameter, and occurred around 300 million years ago. The asteroid that caused this was thought to be
between 10-20 km wide. ANU Planetary Science Institute postulate, that it is possible this impact was part of a greater asteroid "Cluster" that may
have hit Earth around 360 Million years ago, causing mass extinctions......of what life? who can be sure....
Either that, or it was caused by a space war between Human and Reptilian aliens....
. 
