I am now hearing this more and more in general society. My daughter has picked it up, I think from school. I heard it on an NPR report on Monday. I've started to notice several of my friends doing it. I even caught myself doing it the other day.
My hypothesis is that this is the ultimate fate of ending every sentence with "y'know?" I think that the speaker wants to make sure that the listener is following and doesn't disagree. Back in the 1980s, lots of people would use the interrogative "y'know?" at the end of sentences to provide that opportunity to check in, but now it seems to be done with just intonation.
But I have to say? This drives me nuts?