Traditional media companies have stepped up purchases of internet rivals, with the value of public transactions so far this year standing at nearly $1bn (€824m), more than double the total value of public acquisitions made in 2004.

The deals come amid expectations for continued strong growth in internet advertising, particularly that linked to search. Google's market capitalisation last week rose to more than $80bn, leading the search group briefly to overtake Time Warner as the world's biggest media company.