When convention catches up with the technology, what will be proper etiquette regarding public cell phone use?

I am not that old, and even I find myself grousing like a grumpy old man when people let their phones go off at a wedding, text while walking down the street (and into me), and talk in a loud voice to the invisible (sort of the way schizophrenics do) as they meander down the aisle at the grocery store.

I am a bit rough around the edges myself, but I can hardly believe how rude it all seems to be.

Someday, social convention will catch up with technology. What will be OK cell phone behavior? What will be inappropriate?