Thanks for the input thus far, Josh and Mark. But this just isn't limited to a "contact form". Let's say our sales teams are using CRM like they should - as a sales database to manage their contacts. So of course, they would enter all of their key contacts and decision makers at their accounts (and prospective accounts) as "contacts" within CRM. Marketing can then use this master contact/relationship database (vs. purchasing a list - which, as you know, is not the right approach) to market against using Marketo.
For example, let's say we hosted a customer event and wanted to invite all CIOs at our strategic accounts. Some of these CIOs have engaged with prior campaigns. Attending this event will push their lead score over the MQL threshold and trigger a "sync to CRM" flow step (defined within our lead lifecycle). Furthermore, with Sales Insight, the sales teams should be able to look at their accounts/contacts in CRM and also see the Marketo activity/history that has occured within those accounts.
Is this not the common approach/use-case of Marketo and CRM at your companies?