Agreed! We are tossing around the same potential solution for our MKTO forms and website built in Drupal. We are getting a bunch of spam/junk leads through select forms. Curious to see what other people do/how to do it.
Until we have a fix in place that prevents these spam leads upfront from entering into marketo/salesforce from a webform submission, we plan to run a Marketo campaign daily that deletes out of Marketo and Salesforce any prospects with a name that contains “http”.