Eu penso que estar exposto a língua é uma boa ferramenta, por mais que não entendamos, estamos expostos. Depende muito da maneira que a pessoa estuda uma língua. Eu estou de acordo com você, caso sejamos iniciantes ou sem muito conhecimento das expressões idiomáticas, ver estes vídeos pode ser pouco satisfatório. Tenho alunos de português avançados que falam melhor que a população geral do Brasil (em termos de coerência, gramática e etc), porém não conseguem entender nada em um simples vídeo onde haja brasileiros conversando no dia-a-dia. 

Yeah It's perfect. I've improved my English a lot from watching north american youtubers. Good Mythical Morning is a nice example.

In my opinion all kind of exposure to a language you are learning is good, you re  getting used to the sound of the language, also it benefits your vocabulary and pronunciation. I am gonna check that  Porta dos Fundos for sure, I was once already looking for a YouTube chanel in Portuguese myself, but I at the moment I am watching from time to time  somekind of "beauty" channel. 

I like this chanel http://youtu.be/GClwSA1vTS4 and I ve found the "easy Portuguese" very useful as the video comes with subtitles, though the pronunciation freaks me out, I've never heard that kind of "r". 

Honesly, I have no idea what is the most popular youtube in chanel. 

I am using Semantica-Portuguese.com  It uses soap-opera type stories, broken up into 3-5 mins with optional subtitles and a discussion type breakdown to teach, as well as little grammar lessons.  It's really good 

Hi, my dear

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Miracle