However, lots of teenagers will be glad to be on google+, I've felt extremely frustrated at not being on it not because it's a "hip" social site, but because of google's constant integration of google+ into everything. It was like going to disney-land without seeing Mickey Mouse, so I hardly think the complaints would be justified.
Also, not to forget lots of teenagers are tech-oriented, let's not forget how apple and Microsoft started!
Also, not to forget lots of teenagers are tech-oriented, let's not forget how apple and Microsoft started!