Notifications (Facebook style): are they a trend?

[Just a sorry before start, I'm brazilian and english is my 2nd language then i'm sorry for errors :P]

So i noticed today there is a trend growing around notifications.. some few sites are implementing them and I think its great! Seriously how great could it be if there was a 'little planet' in forums, blogs (comment answers) etc. Even here in HN it would be good. Unfortunantly I'm not a coder or anything (yet) so I can't make this happen in a real world situation and don't even know if it's THAT hard to make for e.g a wordpress phpBB, Vbulletin etc. plugin with this pourpose.

What you think about these notifications at all? Do you think like me? Waiting your opinion!