I wouldn't say it's OK, but in the same breath I will also say that not signing for a package is by no means a guarantee that you cannot be busted. The old return to sender and no sign tricks are well-known and LE will often get more info on you than just a signature if they want to bust you. If they want you, they will get you, period.
If you haven't read it yet, I highly suggest reading Legal Muscle by Rick Collins. I ordered it from this site, and it was the best $35-40 I have ever spent. Plus you help to support this site (and Rick) which provides the best info on the net.