[pmontra]

Partly true, because if they try with another browser and get a good result they'll blame the browser and not the website. In this case, they'll probably say the the new Firefox broke YouTube. See one of the comments at www.pclinuxos.com/forum/index.php?topic=135323.0

"i'm getting a lot of corrupt unsupported browser when accessing video on other sites, so i'm using chrome. i can't figure out if it's flash or firefox but i'm tired of opening the hood, i'm done with FF for now"

Most of them looked for a workaround and spoofed the user agent, but they are the kind of people that fiddle with settings. Normal users probably either don't notice or change browser.