@somedude:
There's no DRM in my PDA and I've still got TomTom on it (bought it twice, the second time was an upgrade). There's still a key though, so it's not copyable. It's linked to a serial number in the PDA, in a very non-obvious way.

To get the same level of non-copyability you only need a serial number in the N900 as well. And there's a BT id, for example, or the wi-fi mac (A mac address can usually be changed, but this has been shown to be very impractical on the previous tablets at least). And in the N900 maybe it's even possible to use the IMEI as a serial number.