It goes beyond merely blocking sideloading.

I had one reserved (but put down no money) and ignored the calls to come in and pick it up once the investigations at xda-devs showed that the unit was using the HS model of the OMAP4 with everything signed.

Whole thing is secure. Signed bootloader, checksummed kernel. Totally not worth the time of anyone interested in this sort of stuff. On the other hand, I've had a decent amount of success working with Stskeeps on the Nook Color. Maybe something will (finally!) come of it in the next few weeks. Maybe.