Our websites are getting hammered by spammers scanning for contact forms, tossing some stuff into the fields (cialis, viagra, blahblah) and submitting the form.

The web/marketing team says they do not want to implement a CAPTCHA program to the websites, in fear of losing potential clients. So that option is out.

Any ideas on how to make it harder for spammers when using a Contact Us form on a website? I already suggested at least making the "Phone Number" field only accept valid phone number formats (no words). So that may help, but doubt it.

Any experience out there? Thanks