The best thing Decoy has going for it is its instant speed use of avoiding a tag. Decoy allows the runner to take the tag a SEA Source would give in preparation for a double Scorched Earth and instantly avoid it, protecting them from the inevitable block explosions that follow. It has also been used for cards like Activist Support to protect it long enough for that bad publicity to fire.
Its real weakness is the single use it has. Tagstorm through the likes of Midseason Replacements makes it a useless protection, and other methods of tagging are so prevalent that a single use won’t protect when the time comes for the corp to make use of those tags.
(Written during the meta of The Valley/Breaker Bay, part of the SanSan Cycle. For more reviews like it, visit wyldside.blogspot.com)