Because Capcom has asked media sites to take it down
http://ps3.ign.com/articles/636/636991p1.html
"Citing an official press document from Sony's PlayStation Meeting 2005, Capcom asked Internet publications to remove any sign of movies or stills taken from the Resident Evil 5 trailer. According to a company official, the trailer was never to be filmed in the first place and will be aired officially in the near future. No real window of time was given, however."
http://ps3.ign.com/articles/636/636991p1.html
"Citing an official press document from Sony's PlayStation Meeting 2005, Capcom asked Internet publications to remove any sign of movies or stills taken from the Resident Evil 5 trailer. According to a company official, the trailer was never to be filmed in the first place and will be aired officially in the near future. No real window of time was given, however."