I was just wondering if anyone could point me in the right direction of how Marketo can recognise if someone is already in your CRM, allowing them to access the content instantly instead of filling in a form.
Brandwatch can be used as an example of what I am referring to just to add some clarity.
In your Marketo Form asset in the Settings Section, there is a choice for "If known user show:"
By default, that is set to "Form" Meaning, if a known user shows up, they still get served the form. The other option (Custom HTML) lets you define something different for known users. What we do (and others) to remove friction for known users is instead of showing the form, we use that second option to show the form submit button with some custom text. Depending on your specific desired use case, you could have that text say "View Content" or something instead of your usual submit or whatever your form button says.
This DOES still require the user to click a button, but no form fields/completion is required. What I like about it is that the activity still comes through as a form fill activity in Marketo, so your lead scoring and/or sales alerts for people filling out those forms continue to work as expected, but the user's experience is much quicker/easier.
Screenshots below of the place where you can enable this in Marketo form assets as well as what you'd need to put in the custom HTML option in order to just show the submit button.
Hope this helps!
Unfortunately, this doesn't take into account the cases (which I think Ash meant to include) where
Case  can be accomplished with the Lead Lookup Form pattern.
Case  is pretty far afield, though; you'd need a public, non-DoS-vulnerable way to look people up in CRM, which most people don't (and most likely shouldn't) have.