Many times we get spam e-mails from the contact us page and the best option to stop the spam e-mails is to put captcha image on the contact us page. Still captcha image feature is not available for contact us page in nopcommerce project and i think it won't be available in 1.9version also.
For those who want captcha image on their contact us page, here's the solution which i posted on my website:
Somethin similar should be used when the " Allow anonymous users to email a friend" option in the Other Settings is selected
You can add captcha image in the same way like i added in contact us page. For this the page you're looking for productemailafriend.aspx and see it's module in "Modules Folder" and make the modification in the same way. I haven't tried it but it should work fine.
http://web.archive.org/web/20120202223947/http://strivingprogrammers.com/boards/t/52/how-to-add-captcha-image-in-contact-us-page-of-nopcommerce-18-solved.aspx Captcha in Contact Us is available out of the box in v2.4+