Some believe powerful vested interests, including the government-appointed "political agents" that rule the agencies, have no desire to see parties challenging their influence.
"We didn't have tweeters, bloggers and legions of minor celebrities to challenge their influence," said André Leon Talley, Vogue's editor at large.
It's difficult enough to challenge their power, wealth and political influence without the likes of Climate Week giving them an easy reputation boost - including, in this case, six extra months of free advertising all over the Climate Week website".
Many authors blurb down, endorsing former students (Joyce Carol Oates on Jonathan Safran Foer), less celebrated writers working in a similar vein or up-and-comers who validate the blurbers' own influence without challenging their supremacy (Salman Rushdie on Zadie Smith's "White Teeth" and Kiran Desai's "Inheritance of Loss"; Chinua Achebe on Chimamanda Ngozi Adichie's "Half of a Yellow Sun").
Dads are wielding influence with advertisers to challenge their portrayal of men as blundering, amateur baby handlers.
We challenged the influence of Natalizumab on T suppressor frequency and function.
Increasingly, however, the ability of rangelands to continue providing these services is challenged by anthropogenic influence.
It will both challenge and influence the development of policy from the outset.
In 1399 the Ottoman sultan Bayezid I, challenging Mamlūk influence, installed Dulkadir Mehmed as ruler.
Finally, the supply revolution in the United States and Canada will challenge the influence of the OPEC cartel, as even its recent publications have acknowledged.
