how do they implement the copyright thing?

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i uploaded some photo slideshow with music on it (no slideshow is good without music, we know that) but they blocked one of them informing me that the music i used was copyrighted. i am aware of that and even put disclaimer. how come they only block copyrighted materials from CWG? the one i uploaded 3 yrs ago and had about 150 views was just recently blocked? they will ask you to pick from their pre-selected music to bring your video online again. is that their way of promoting the company? if using and/or uploading copyrighted musics/videos is not allowed, then, they should block almost half of their video database regardless what company owns it. wouldnt it be fair? what do you think?