Youtube - matched 3rd party content

I've just got this notification on the last clip I uploaded - the cover of Imagine. Is this normal and is it a problem at all? It seems to mean they can stick ads on it.

(ps - is this the best place for this? apologies if wrong forum)

I believe it means they put ads on it, but can still remove the video at any point if the copyright holder complains.

Petey

They can do it with any cover tune you do. I've got maybe a dozen cover tunes on YouTube, but for some reason only two are flagged that way. It doesn't seem to make any real difference. I think you're fine as long as you're not making money off someone else's song and not paying royalties.