I agree that courtesy and manners are becoming lost. But, I do not find this to be a factor of age or generation at all. Someone who is in my mother's generation (65+) is just as likely as someone in Generation Y to not acknowedge a gift that was given, for example. I find it a factor of the general state of the way things are.
The only thing i can do is to remember my manners, and hope someone will be motivated to do the same. My teenage son has excellent manners also.