What's the opposite of celebrity endorsement?

I mean... what's the official term for the situation where a person in the public eye and a key influencer of significant amounts of people decides put down or generally voice a negative view about something?

Celebrity derisement perhaps?

Now I've previously commented that Celebrity is not to be confused with influence, but when a person has both of these and they start giving their opinions, people listen and act accordingly.

This was once-again brought to my attention yesterday when Rory Cellan-Jones mentioned Stephen Fry's negative Twitter comments about his new Blackberry Storm on Twitter. It seems that one man is able to make a difference in the successful launch and selling of a product.

The topic must therefore get around to the question of "which celebrity derisement do you need to avoid?" or "which key inflencer's negative sentiment causes the most impact?". How do you find this out?

A theory:
By understanding, measuring and plotting your company's corporate social graph, you can specifically identify your celebrity influencers as well as other key figures (journalists, officials, etc.) and appropriately deal with their positive and negative endorsement.

Collective endorsement

Alastair Duncan has recently used the term 'Collective Endosement' in his blog posting 'Communities are the future' and I think it is a very well chosen phrase. It sums up how specific groups bonded by a shared sentiment (and not necessarily geography) flock around a particular idea.

Alastair also poses the question:

"Will communities be the dictators of content in the future?"

and he asks if these communities could gatekeeper the outcome by this collective endorsement.

I'd like to take this idea a little further and state that I don't believe it will be entire communities that will control this sentiment all the time and that key influencers within these communities will often lead the collective embrace (or attack).

However, unlike the concept of The Tipping Point, where these are super-influencial social magnets.... these people could be normal, everyday people. The downside is that it therefore makes it far harder to understand the dynamics involved and plan your influencing strategy accordingly.