I often encounter Windows users than love to spew hate toward Linux although they themselves often think it's an application you can install, isn't graphical at all, is dead for the desktop, can't run more than one CPU at a time, is only used for servers, or doesn't follow standards - what a joke!
So to all those people, here is a blog entry just for you... Linux powers 850K new Android devices per day, most of 700K new televisions purchased per day, 8 out of every 10 financial trade, 9 out 10 world's supercomputers, the $10B CERN large Large Hadron Collider, Lockheed Martin's Nuclear Submarine, Japanese high speed train, and the US air traffic control system.
Most website are powered by servers running Linux and opensource, these sites include Google, Twitter, Facebook, Wikipedia, Travelocity and Amazon. In actual fact in recent years 8000 developers from 800 companies have contributed to the Linux Kernel. Red Hat (a billion dollar company) just focuses on Linux for business, both server and desktop, same goes for Novell with SuSE.
Linux has a few full GUI desktops to choose from and thousands of applications, including the ability to run many windows applications. So who uses Linux as a desktop? Google has 10K, City of Munich 14K, IC bank of China changing to Linux in 20K branches, Czech Post 12K, France's police dept to have 90K by 2015, Macedonia Education has 180K, Germany students with 550K, Novell 5.5K+, Peugeot 20K, DreamWorks has 1K, FNB Bank (the most innovative Bank in 2012) run 12K, to name but a few...
In 2009 Microsoft CEO Steve Ballmer indicated that Linux had a greater desktop market share than Mac, stating that in recent years Linux had "certainly increased its share somewhat". Just under a third of all Dell netbook sales in 2009 had Linux installed.
That is an insane amount of business powered by Linux, at the end of the day using what works and being able to change with technology will highlight those IT people worth their weight in gold!
Linux developers also follow international standards like the RFC documents, if this was not the case Linux would have been an isolated and limited operating system, something it definitely isn't. Linux often has to even adapted to accept non-standard methods simply enforced by other companies.
Some other devices which run Linux you might be using/interact with: ATM machines, Kiosks, Slot machines, ADSL/Cable modems, Traffic Lights, Carrier Class Network Equipment, VoIP Phones, IP CCTV cameras, car computers/radios, fridges, and many many more!
All stats are from places like wikipedia and other trusted sources, if you find a wrong figure or want something added to the above please let me know...