Is a tactic used to discredit a product or service by creating a negative perception of it through lies or other means. See http://en.wikipedia.org/wiki/Fear,_uncertainty_and_doubt

Note that today, with so many bloggers and “thought-leaders” on the web with decent-sized audiences, it wouldn’t be too difficult for a company to find fairly influential people willing to say negative things for money. If done effectively, someone doing a quick web search for the new product or service might find a lot of negative opinions about it. Fake online reviews could also be employed.

Here’s a fairly recent (and well documented) incident of FUD-like behavior: http://www.ripoffornot.org