Joe Stewart, director of malware research at SecureWorks says that sometimes people who receive messages which they recognise as phishing emails decide to retaliate by completing the offered form with incomplete or incorrect information.  If they do this - especially if they use the word 'phish' or swear words in what they enter - they can be subject to virus attack.

In such circumstances - unless all of the latest security patches are fitted to their operating system, browser and add-ons - their system could become a source of phishing emails, the recipients of a destructive virus or be subejcted to false warnings of infection. 

The last might be sufficiently convincing to cause useless software to be bought which then brings viruses with it that compound the problems.