A few good points have been made (but need a few editions), and some dumb points have been made. Let's run through them:
1. The SS-N-22 is a hush-hush subject because it basically reduces our carriers to floating targets
Not the case. Details about the SS-N-22 (commonly called the Sunburn) are unclassified. Every ship in the US navy has tactics to defeat it, though obviously some classes of ships are better at it than others. Actually, the missile in the video behaves nothing like a Sunburn; it appears to have satellite guidance, Over the Horizon (OTH) targeting capability, and a terminal sprint vehicle. Thus, it's closer to an advanced Sizzler missile (SS-N-27) http://en.wikipedia.org/wiki/SS-N-27 than a Sunburn.
2. Somebody mentioned Exocet missiles and their relative effectiveness. Exocet missiles, to the US navy, are kids' stuff. My ship (an Arleigh Burke-class destroyer) is basically armed to the teeth and can shoot one own without so much as a second thought, but even ships built with self-defense as a third priority are in no real danger. Exocet was a threat when they made the movie Top Gun, but not today.
3. Someone mentioned targeting requirements. This is a good point. If a ship expects to use this in an anti-ship role, it will either have onboard radars for detection and missile control (US is the only navy that has a radar which does both), or receive targeting information from another ship/sub/satellite. In any of these cases, the targeted ship can detect the radar, and any missile control radar it detects is considered a hostile act under international law and triggers the captain's right of self defense (read: he can shoot at you if you point missile control radar at his ship). Also, any merchant ship leaving port with a bunch of innocent container boxes PLUS high-powered missile control radar is, to say the least, suspicious.
4. Several people mentioned the Phalanx Close In Weapon System (CIWS, pronounced See-Whiz). This is the last resort for most classes of ships. It can only shoot out a few miles, but it's very effective when it does fire. If this system is firing, by the way, then the missile has somehow made it past your three to four other layers of defense, not even counting soft kill options like jamming whatever active radar or semi-active/passive sensor is guiding the missile.
5. A few people mentioned the ethical issue of arming merchant ships. This is always considered in warplans, from low to very high scale. Bottom line is that it's a dumb idea that will get you one free shot and then cost you your whole merchant fleet.
6. Ignoring all of that, no matter how effective any weapon system is, at least in a shipboard environment, you only get one free shot. After that free shot it becomes a hot war scenario and every ship captain will change from "ask first, ask again, check three times and only fire when fired upon" to "ask once and if you think he's hostile, shoot." It can even go further to "Check to see if your'e sure he's a friend, and if you can't tell, shoot." At that point the name of the game is ship detection, not missile technology.
This weapon system doesn't revolutionize warfare at all. Business as usual.