Despite all the warnings if you upgraded your iPhone to the latest iPhone OS 3.0 Beta without a developer account you must be locked-out from normal phone functionality, downgrading your iPhone to an earlier version is pretty straight-forward but downgrading your baseband (which is responsible for the unlock being not functional anymore) is not possible with newer versions, You can downgrade iPhone OS 3.0 To earlier 2.2.1 version using the following guide.

Users have now found a way to install and use iPhone OS 3.0 Beta on iPod Touch without an developer account, the hack involves using the iPhone OS 3.0 Beta .IPSW restore file with iTunes blocking the applications access to internet via firewall.

The trick is that iTunes uses an active internet connection to verify whether the current device using the BETA OS is developer registered or not, if it founds non-developer registered device using the BETA OS iTunes syncing is disabled, this simple check can be easily bypassed using the hack described next.