The company recently implemented digital fingerprinting technology to identify videos that the company has been asked by the copyright owner not to post on the site.
The technology compares posted clips with reference videos supplied to YouTube for analysis.
But the technology doesn't work as well with batches of different clips with different characteristics, even if the clips are all from the same event.
"That's more difficult when you are dealing with a live performance because the sound quality is poor and the image quality is similarly poor and probably very varied according to who was filming and where they were in the crowd," Robertson said.
Video clips of legendary rock band Led Zeppelin's reunion show in London on Monday are reappearing hourly on YouTube despite efforts to remove the material due to alleged copyright infringement. YouTube warns users in its "help center" that they may not own the rights to upload concert footage to its site.
Some links to videos of the band's performance lead to a red warning that says the video has been removed "due to a copyright claim by Warner Music Group."
The situation marks another clash between copyright holders and YouTube, which is owned by Google. Entertainment giant Viacom sued Google for US$1 billion in March over the unauthorized uploading of video clips from its TV shows and movies.
Since then, Google has taken steps to address complaints about material under copyright posted on its site without permission.
YouTube's policy is to remove material after it is notified of the URL (uniform resource locator) of the offending clip, according to a spokesman for the site.
YouTube puts the onus on the copyright holder to notify it, which is one bone of contention in Viacom's lawsuit, Robertson said. However, the notification policy complies with the U.S. Digital Millennium Copyright Act as well as European copyright law.
YouTube would not comment specifically on how many Led Zeppelin clips it had removed because of alerts from Warner, which holds Led Zeppelin copyrights.
But the enormous interest around Led Zeppelin's reunion show means the clips could prove difficult to keep off the site. New reports said more than one million people worldwide entered a lottery to buy some of the 20,000 available tickets, which started at
Most of the video clips are grainy with tinny sound, but it hasn't stopped fans from gushing about band.
It's "as if they never aged," commented one person on an eight-minute clip of Led Zeppelin performing "Kashmir," which was still on YouTube as of Wednesday morning. "They are the greatest band ever."