In this film, extra terrestrial contact is made, with the ET's transmitting the blueprints to a massive engineering project—supposedly for us to build. After studying the schematics it is determined that it is the outline for some sort of transportation device for a lone passenger. The exact means of transportation is unknown, as is much of the science behind the radically advanced technology.
There is some debate about the safety of embarking upon such a project, including worries about it being a possible Trojan horse or doomsday device, but ultimately the fears are set aside and the device is built at a cost of a quarter of a trillion dollars.
As I reflect on this film, however, I believe the decision to construct the device was the wrong one. Rather, the precautionary principle should have been invoked big time. In general I'm not a big fan of the PP, but in this case I think it would have been warranted.
Without knowing the nature of the transmitting ETs themselves, or even if conscious entities were actually transmitting the signal, there's no way we could predicted ET's true intentions. It very well could have been a Trojan horse; the device could have been deliberately designed to look like a transportation device to fool us into building it, only to turn out to be something far more nefarious instead—like a doomsday device, for example.
Why would ETs do such a thing? Well, the transmission could have been viral. Imagine a malevolent or paranoid civilization (or group or individual) determined to wipe out intelligent life across the Galaxy. They set up a bunch of beacons across the Galaxy that transmit the evil code.
As precedent that intelligences are capable of such a thing, people write viruses here on Earth for no good reason. Perhaps signals such as these are the ultimate manifestation of computer viruses—one information system finding memetic compatibility with another and infecting it. The trouble with such a scenario, however, is that such a code wouldn't replicate and re-transmit. But if the source transmitter remains intact, it would be the Typhoid Mary of civilizations.
So, rather than build the device on sheer blind faith alone (i.e. Not knowing how the technology works, not knowing exactly what the device is supposed to do, not knowing who transmitted it, not knowing why it was transmitted....), I would have suggested that the extra terrestrial schematics be studied, reverse engineered, and modeled to the point were we felt comfortable enough to predict as much of its effects as possible.
And then we could build it.