Crypting services are the primary reason that if you or someone within your organization is unfortunate enough to have opened a malware-laced attachment in an email in the first 12-24 hours after the bad guys blast it out in a spam run, there is an excellent chance that whatever antivirus tool you or your company relies upon will not detect this specimen as malicious.
In short, as I've noted time and again, if you are counting on your antivirus to save you or your co-workers from the latest threats, you may be in for a rude awakening down the road.
Does this mean antivirus software is completely useless? Not at all. Very often, your antivirus product will detect a new variant as something akin to a threat it has seen in the past. Perhaps the bad guys targeting you or your organization in this case didn’t use a crypting service, or maybe that service wasn't any good to begin with.
In either case, antivirus remains a useful — if somewhat antiquated and ineffective – approach to security. Security is all about layers, and not depending on any one technology or approach to detect or save you from the latest threats.