You can turn off the switch in Authorize.net to decline transactions where the AVS do not match. That way the system will notify you that the AVS did not match but also aprove the transaction.
So you can in fact process sales without AVS matching and that's not a problem (many merchants do it).
What they do is call the customer directly if the transaction looks suspicious.
If you would like to discuss this via email contact me any time at
msinfo@merchantseek.com
Joe