Do you native speakers always understand?

Hi,
do you native speakers always understand what people say on TV, on the radio, in movies, in songs, etc.???

In Italian, unless people start to talk in a regional dialect (not accent, I said "dialect"), I think I always understand what they say on TV, radio, etc., if I listen carefully.

But... it seems to me that English has very weird accents sometimes. KFC turns into K-eye F Say, life into loy-f... bottle with a glottal stop... Ok, my listening skills are not good, but when I hear weird accents, if I understand something it is just because I guess from the context.

So what happens to you native speakers? Do you always understend everything if you pay enough attention? And if not, what is it that you usually don't understand completely? I'd like to hear your opinions on this, thanks

Do you always understend everything if you pay enough attention?

Every syllable!    As long as it's just some regional variant within the U.S.  The Brooklyn accent is an exception.  I find that one difficult.  Australian accents stump me, too, sometimes.

CJ

No, sometimes we meet other native speakers with accents we find quite difficult to understand.  I've got a pretty good ear and enough imagination to usually fill in the blanks so I can usually manage, but some people really can't understand an unfamiliar accent. I was at a restaurant with a few friends and our waiter had some sort of northern English/Midlands accent. We had to get him to repeat himself a couple of times. I quickly tuned in to him and was ok but I had to 'translate' for my friends who simply couldn't understand a word he said.  I find some of the UK accents more difficult to understand than any of the US/Australian accents I've heard so far.

In my first job I worked with an Irishman and we never really learned to understand each other properly. He was my supervisor and we got by with a lot of miming. It only really caused problems with names. He never learned what my real name was and used to call me a mangled approximation. Our boss used to get really cross with him about it and try to teach him my name (not an unusual name) but he could never get it. On reflexion, I wonder why I didn't just write it down for him? We were working with horses and I never learned what one of them was called  as I couldn't understand the word he was saying - was it Lucy? Youthy? Youthful? Yootha? Loosey? Loothee? Blue-sea? You-see? Everything I tried was met with a frustrated no, shake of head. In the end we gave up and he called the horse whatever her name really was and I called her Lucy.

Hey, I almost forgot I posted this! Thank you so much for your comments.

I see Jim understand everything, even Martian dialects. I believe that's a great ability, I think it is due to many things... for example, I know jim knows some foreign languages very well, and that could have helped develop that ability, because he's had to learn several different "sounds" in order to learn foreign languages. So maybe he's got more trained ears...

And I see that the one who has trouble is Nona. Your stories are funny, especially the one about the Irish guy, LOL. I knew I would get an answer like that from you, Nona, because I know some British accents are very weird. Actually, I thought of opening this thread after hearing a British accent (I don't know what accent though).
I was reading another thread, and a guy mentioned a movie where the characters were supposed to have a particular accent. So, you know what I did? I got interested, I wanted to hear them, and so I took a look on Youtube.
So, you guys now go to the movies or just buy a DVD or something and start to watch this:
[link]

What crosses your mind while watching something like that? You have to pay attention?

That's a Liverpool accent. I can understand them just fine but I could understand people who aren't familiar with the accent having problems.