The NYTimes has an article "NBC’s Web-Only Episodes Offer ‘The Office,’ a Little at a Time" which looks at the phenomenon of putting TV shows on the internet and issues such as advertising and other distractions when viewing TV online.
I think this is definitely an Emerging Media issue that is at a very early stage. Networks are trying to compete with the likes of YouTube and Google Video to attract the eye-balls of the youunger generation, who spend most of their time online. How succesfull they are will largely depend on how well they execute the migration of TV to the Internet.
Their early attempts seem to be lacking the very things that Internet users crave for, namely control over what they are viewing. If viewers are forced to watch advertisments and not allowed to skip them, it will discourage many viewers from coming back for more.