One problem with contact forms is that it is easy for people to pose as someone else simply by entering someone else email address. Additional if there is any "loose code" with the contact form, it is possible for hackers to hijack contact form to use as their own spam machines.

See what is meant by "form hijacking" in these articles...
http://www.anders.com/projects/sysadmin/formPostHijacking/
http://www.softswot.com/form-hijacking.php

Instead, we preferred to use a mailto contact link that is Javascript constructed (so that it can not be harvested by spambots).