For what it's worth I just tried a GRC Port Scan against a Kobo Wifi
GRC Port Authority Report created on UTC: 2010-12-28 at 14:13:43
Results from scan of ports: 0-1055
0 Ports Open
1051 Ports Closed
5 Ports Stealth
1056 Ports Tested
NO PORTS were found to be OPEN.
Ports found to be STEALTH were: 135, 137, 138, 139, 445
Other than what is listed above, all ports are CLOSED.
TruStealth: FAILED - NOT all tested ports were STEALTH,
- NO unsolicited packets were received,
- A PING REPLY (ICMP Echo) WAS RECEIVED.
So at least the standard service ports are closed.
In fact, using nMap across all ports show they are all closed too, so it does not look that there is any way to initiate a transfer to the Kobo from an external device.