There's a lot more of a cultural and technological revolitionizing effect that Smartphones have brought to society than just Facebook anywhere; although that's a part of it. If it's not obvious by now, iPhone is at the forefront of that industry. Facebook has become an incredibly useful communication tool, and it's ubiquitous.
I think iTunes U is worth mentioning as another example (used by something like 300 million people) which as of last year has dozens of Yale courses available now too, is an important part of that too. Essentially, you have free material from Libraries, Museums, and tens of thousands of lecture series (typically 24-36 lectures, 45-90 minutes each per course) available in video and audio format, from over 800 Universities. All material is free - this is my favourite app, I listen to lectures now much more than I do music; anytime, anyplace.
Before we had books. Then we had TV and phones. In the 80's we got personal computers, in the 90's we got the Internet, and in the... 00's(?) we got Smartphones which allow us to take essentially everything mentioned above everywhere. Obviously PCs still have their place considering their bigger and capable of much greater power consumption, but Smartphones (especially with Cloud services) have become an important extension of that; and can also do most things that most people want to do (in terms of communication, reading, media, and other applications) on their own.
-Insert Inspiring Quote-
