Dummy Box is essentially a huge middle finger to Skorpios. One thing they like to do is Best Defense one of your Sacrificial Constructs, because it has a play cost of zero credits, followed up by a Hunter Seeker to trash and remove your programs from the game. Dummy Box says "bollocks" to that by costing 1 credit, so it is not susceptible to the same line of play.

But even when not facing Skorpios, this card is extremely versatile. Got all your breakers installed and have a spare SMC or Magnum Opus in hand? Keep your programs safe from cards like Ichi 2.0 or Tithonium! Corp is trying to use Voter Intimidation to trash a highly valued resource like Beth or Film Critic? Trash a resource you don't need from your hand and you have Fall Guy for days!

Does that make it worth a place in your deck? Eeeeeeh, possibly? If you expect a lot of Skorpios, this is definitely a solid include and if you like to play safe, one Dummy Box never hurts. But I would not say it is a must include in most circumstances. 2 influence is also enough to make non-shapers think twice about including this, especially since deck spaces are super tight. Also, since this is a resource, it is not very good at protecting your resources if you have trouble shaking tags or plan on being tagged. Wireless Net Pavilion might be better in this case.

One more thing to keep in mind is that Dummy Box does not help you protect Clot, Tapwrm or other viruses when the corp purges. Counter-intuitively, the runner is actually the one who trashes cards from a purge, while Dummy Box clearly states the corp has to be the one to trash something.