The upward inflection
That's the one, I can never remember the name of it. It's possibly the worst thing I've seen/heard happen to the English language in my lifetime.
I'd say it's as many as 8/10 people that do it, it's getting quite serious, from teenagers right up to OAPs. With some people it's like they don't even know they're doing it.
I just wish I could tell them how ridiculous it makes them sound, which reminds me of another phrase that seems to be bandied (not banded) about these days - 'trend sheep'.
Here's another one that's just come to me - people who use 'a lot' instead of 'a lot'.
'We're all a bit on tenderhooks', ******* 'tenderhooks'?! Wtf is a tenderhook?