2 of 2 people found this helpful
It is pretty unaccurate. See my answer in a recent post:
Inferred info is collected from WhoIS public database, from the IP address of the visitor. It is completely automated, you have nothing to do and BTW, the fields are not modifiable in Marketo.
The quality of the info is uncertain, as most often, for small business, the WhoIs will give you the ISP and for larger ones, the use of VPN's make the IP address often not reflecting the real location of the person.