the ide is…
spambot usually only parse html and never read any js/flash.
so, they can not see your form. so, they can not (ab)use your form.
also very important: never have any html link to your form or any script you use to send email.
and dont even tell about your form/mail scripts on your robots.txt
coz ugly spambot will actually follow any disallowed stuffs in your robots.txt