To Serve Man
In the Damon Knight short story it turned out to be a cookbook.
With the billions of earth-like worlds in our galaxy alone and the strong likelihood that many millions have developed viable technology based civilisations, we must also look at the time factor. Any civilisation older than our own is bound to have developed technology superior to our present level. Look back at where we were 200 years ago compared to now and then extrapolate the technology expansion for a thousand years. Sir Arthur Clarke's 3rd Law states that any sufficiently advanced technology is indistinguishable from magic. The technology available on this planet in 100 years could be at that level, in a thousand years it may be as difficult for us to understand as a caveman when we try to explain to him what wifi is. So imagine how a civilisation a million years older than ours would look to us - we would struggle to communicate let alone understand the technology.
I am certain that given enough time any civilisation will develop faster than light travel be it "warp drive" or something we cannot imagine yet. So the ones that are a few million years ahead of us almost certainly already have it. (to those who say "impossible" I quote Sir Arthur C Clarke's 1st Law "When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.")
So it is quite possible that sufficiently advanced beings may have already visited us or are about to pop in any minute. It is also very likely that they would be so far ahead of us that they would regard us as we regard animals and consider us not worthy of contact, and it is just possible that they may even have engineered us thousands of year ago as part of a stock breeding program that will result in our demise and appearance on their dinner table. Or perhaps the "Predator" movies were nearer to the mark and we are actually a hunting preserve.
The seti project when it finally finds the right wave length, or perhaps when we discover telepathy or subspace communications, could be responsible for sending out the message that we have matured enough to be ready for culling. Effectively "Here we are, come and eat us".
It would be nice to make contact with nice friendly aliens only a little ahead of us along the technology curve who are falling over themselves to give us a cure for cancer, cheap energy, and the secret of immortality, but the odds are against it.
I have often read SciFi writers describing humanity as being like the Native Americans and the Aliens likened to the Europeans who came and took their lands and gradually wiped them out. I think that is a gross overestimation of our relative importance, we are more likely in the position of the Native American Buffalo.
BTW Apologies for quoting Sir Arthur C Clarke, but he was the man who invented the communication satellite.