While reading an article on UFOs, I found the following comment and was intrigued.
"UFOs are mechanical computers
I was invited to join a government study of unidentified phenomenon. I believe the study was classified, but I was never asked to sign a non-disclosure. I was only peripherally involved in the study. But what I do know is that there are objects near the earth that did not evolve on the earth. There are no "aliens" inside these craft, as everyone assumes. Instead, what the current hypothesis says, is that there are trillions (literally) of highly advanced computer-like structures throughout the universe. They are mechanical in nature, and have intense processing power. They probably operate using quantum calculation. They are not "visiting" the earth any more than they are "visiting" any other planet. There are simply so many of these things throughout the universe that they are near just about every planet. The hypothesis is that they self-replicate, and that they may be networked together in some loose fashion. There is evidence that they have been around since near the beginning of the universe.
The reason for secrecy is two fold. First, we don't know if they are a threat to humanity. They do not appear to be a physical threat, in that when one of them enters the atmosphere it does not attempt to interact with humans or human technology. In fact, they explicitly avoid collision with aircraft if a plane or jet comes near one. The threat is believed to be psychological rather than physical, wherein they may interact with the human brain and influence human thinking through some sort of virtual reality. Many people describe events that they think happened to them when near one of these objects, when other nearby witnesses do not describe the same series of events.
The second reason for secrecy is that many people may not be able to come to grips with the fact that there are "living" objects in the universe that are not based on carbon, and are not based on biology. They are more akin to computers, yet they are just as "alive" as we are, and a lot older, and light years more advanced in knowledge, and maybe even spirituality, than we are."
-Eric of MI
I can't vouch for the truth of the above comment but I do find it very interesting since I am of the opinion that if UFOs are indeed extraterrestrial then they would be examples of advanced intelligent machines.
In fact, any occupants may be created by these machines, perhaps even from our own DNA, as a workforce.
If members of the government secretly believe this to be the case then this might be a good reason for the secrecy surrounding UFOs. The knowledge that UFOs are intelligent machines may be too much for the public to handle.