Preventing competitors from submitting a Marketo form

A competitor most of the time will just sign up with a personal email though to circumvent this.

Do you have double opt in implemented on your site? This would at least stop them entering dummy email addresses to access your data.

When they fill in the form the rules would only be checking that the form has been completed correctly not that the email is a competitors. You can put in checks for certain domain names etc.., some people would block leads from using outlook.com or yahoo.com in the email field.  This would be done through javascript though and not through flows or inputs on the backend. 

You can have rules on the backend that deal with competitors once they enter the system. (Black lists Add Person to Blacklist - Marketo Docs - Product Docs ).

Instead of putting the content on the landing page you can just include a link to it in an email and once they fill in the form you can direct them to a landing page that says "thanks and your content will be emailed to you shortly".  Your system rules would then check the lead and stop the email from being sent if they used a competitor email address.

Thanks,

Gerard