Here's our scenario:
A lead receives an email, sending them to a landing page. On the landing page, is an iframed piece of content. This content contains a token from the lead, that populates the correct iframed content for them.
Then....They forward their email to person #2 ... or, maybe they send the actual Landing Page URL. Person #2 is not in our database.
What I'm hoping is that maybe there's a way to redirect people to another location, if they arrive at the URL and appear to be a new, previously un-cookied person?
If the URL self-identifies the lead (as is the case with a Marketo tracked link, you're not really explaining what you mean by "token" here) then you can't tell the difference between one person who has that link and another.