I'm on a campus network that reverse proxies all HTTP traffic. The service shows my internal 10.x.x.x IP. Just a heads-up that you might want to fix your handling of X-Forwarded-For headers.
Also, I wonder if it handles X-Forwarded-For headers that contain multiple IP addresses, because there are multiple levels of proxying taking place.
Also. No IPv6? How boring.
$ curl ipinfo.io/10.0.0.1
{
"ip": "10.0.0.1",
"hostname": "No Hostname",
"loc": "",
"bogon": true
}