As noted by Jamie, if an anonymous lead has not been promoted to known, it will not run through SCs.
However, if you insisted that certain "interesting" leads run through SCs for some reason, you can create what I call pending leads. These are leads that are identified only by their Munchkin cookie (i.e. their email = their cookie). You would not want to sync such leads to CRM, of course. Nor would you want to create a pending lead all the time because -- and this is important -- pending leads count against your Marketo lead limit. But if you used a client-side geolocation service to infer company (which won't be any less accurate than what Marketo does on the server, and probably more so) then you could strategically create pending leads when appropriate.
This wouldn't be too hard to build, but not exactly easy, either (if you're not a developer).