RADB based filters

I was wondering what those of you who are doing RADB/MCI-RR/ANS RA
     filtering were doing about large networks which do not register their
     networks in the RADB. It would seem unwise to simply trust their
     announcements, and even more unwise to simply ignore their announcements,
     so... Whats the common parctice in this scenario?

If they are a customer they _are_ registered no matter how big they
are. If they are a peer then we only do AS path filtering, providers
get free rein, although in both cases I am considering deploying a
filter that doesn't accept announcements for our (static) customers
from either of them.