rocknbil - 6:18 pm on Feb 9, 2011 (gmt 0)
Nah you don't need a captcha, this looks to me like typical link-dropping spam. the concepts here [webmasterworld.com] will reduce it to almost nothing.
More here [webmasterworld.com] if you want to extend it to log your form input in an intelligible format - which you should, so you can see what they are up to. :-)