Well, if I ran a company and could choose between free advertisement and actually getting paid for having others advertise my product, there would be no debate

Nintendo isn't removing their content or telling them they can't upload these videos.  They are just putting their ads on them.

Erm...am I the only one that doesn't have a Scooby Doo what an LPer is..?

Nintendo acknowledged as much when they released their yearly financial statement last month. When they posted losses of 366 million dollars for last year. They also said as much themselves. This is a direct quote from Nintendo.

“Owing to the fact that Wii U hardware sales has a negative impact on Nintendo’s profits, the operating loss was 36.4 billion yen.”

Please Understand. That search engines are your friend. In other words check for yourself first. You will be glad that you did.

"Let's Play"-er.

They record themselves playing through various games and upload the footage to sites like youtube.

They are also causing them to have no monetization on the videos. That is a major problem for many youtubers who do need the money to help stay afloat. some youtubers have youtube as their only job. The long term problem is that these LPers will just refuse to play Nintendo games on their channel. 

So far, the games that have been content IDed include New Super Mario Bros. 2, New Super Mario Bros. U, Super Mario 3D Land, Luigi's Mansion Dark Moon, Ocarina of Time, Legend of Zelda Windwaker and mario Kart 7. All these titles have released in the last couple years or are soon to and are prominent titles. 

Anyone can send DMCA take down, it seems. You can pretend to be Nintendo and ask Youtube to take down stuff for you.

Shoot first. Ask later.

Agreed. It would be worse if they totally took the videos down. That would be a real problem.

I see no problem, also this.

Yeah I'm alright with this, it's their property after all and they aren't taking down videos.