Why? MTV, which brokered music videos into the mainstream, failed to reach an agreement with Universal Music Group & Vevo (the YouTube-esque music video site). Which means none of MTV's Internet properties will be able to show videos from UMG's artists.
This is huge hit for MTV in general because Universal Music Group is the largest music label on Earth, how so? Besides being the largest of the 4 music music companies (Warner Music Group, EMI Group, Song BMG & Universal Music Group). Universal Music Group owns Motown, Interscope-Geffen-A&M, Island Def Jam, Decca, UMG Nashville, UM Latin Entertainment, Polydor Records, Mercury & Island Records... to name a few.
In addition, with over a thousand of big name artists under the sun from 50 Cent to Black Eyes Peas to Diana Ross to Elton John to Eminem to Jay-Z to Juanes to Kanye West to Lady GaGa to Nelly Furtado to Patti LaBelle to Rihanna to Scissor Sisters to Snoop Dogg to Stevie Wonder to U2, etc, because of this fallen deal. MTV will loose ALL UMG web music videos from Universal Music! Even on television, that's if you have MTV2, but even that has stopped playing music videos. Unless, a deal isn't worked out soon, the official web/youtube videos from UMG will stop working.
Source: MTV loses Web videos from Universal Music | Media Maverick - CNET News