Like most social media trends of the internet, teenagers and young adults formed the front lines and propelled Twitter to stardom, and now it's been consumed by the business world.
This trend is neither sad nor happy, good nor bad, it merely is what it is. Myspace went through the same thing; it's still widely used, but by more of a business oriented crowd. There will be another trend for the teens, don't worry.
As for Google... well, soon we'll all have Google bar codes tattooed on our necks so that the Hegemon can find us at all times.

(I'm Brian by the way, I'm new and this is my first post. I'm a landlord and real estate investor, with a legal forms background, and I can't wait to see you all around!)

Cheers,