Fostering doubt is a well known public relations tactic. Phil Lesly, author of a handbook on public relations and communications, advises corporations:

'People generally do not favor action on a non-alarming situation when arguments seem to be balanced on both sides and there is a clear doubt.
The weight of impressions on the public must be balanced so people will have doubts and lack motivation to take action. Accordingly, means are needed to get balancing information into the stream from sources that the public will find credible. There is no need for a clear-cut `victory.'...Nurturing public doubts by demonstrating that this is not a clear-cut situation in support of the opponents usually is all that is necessary' - Philip Lesly, `Coping with Opposition Groups', Public Relations Review, (1992)

from 'Corporate Hijacking of the Greenhouse Debate', Sharon Beder in 'The Ecologist'