Are forms created in Marketo susceptible to SPAM?

Hi Geoff, Marketo has done their best to prevent spam fillouts, but sometimes they do slip through. That said, I would advise against using captchas or other spam prevention methods, and try to weed them out on the backend, as captchas or other spam preventers just result in more (challenging) things for your true form fill-outs to have to complete.

Yes, Marketo forms have improved on spam. I honestly haven't seen this as a big issue in 2 years. What you can do is create anti-spam automation that checks for Blank Leads or BS leads and then delete them. Most firms do this as part of data management.

I agree...you can also set smart campaigns up to catch common fake emails - like abc@xyz or a@a, etc.