Don't want to make anyone paranoid, but I came across this article at http://www.usatoday.com/life/cyber/tech/ctd427.htm. Here is an exert:

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In May, somebody using the name ''Orangemuscat'' declared on the
Yahoo! online message board that Itex's ''current management is blind,
stupid and incompetent.''

The lawsuit charges the author of the message with defaming the
company and its president, undermining the confidence of Itex's
investors, customers and barter exchange members.
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I always thought that opinions were protected as free speech?