Yes, it uses reverse lookup.
So you are using Anonymous leads to flag potential accounts? It is possible that as Google resolves for your landing page, it is hitting your page instead of the lead's IP, so it looks like Google. Not sure of the exact reasons for this, but that could be one of them.
If they do fill out a form, Marketo will look at the lead's IP. Of course, ISPs can still show up here.
That's a good theory, Josh - and makes sense. Unfortunately, these are non-gated pages (no forms - except the final (of four) pages, which is for anyone that responds to a retargeting ad) as this round of advertising is primarily focused on branding and awareness. We have some impressive results thus far (we're using DemandBase - which includes an interactive/drill-down dashboard) - I'm just trying to find ways to drive some additional value to our sales organization with some real-time alerts.