While contemplating alien species and humans interactions, I like to think of the relationship modern researchers have with unique creatures. Lets say a team of researchers found a small island with a new creature on it, lets say it's some species of ant for arguments sake. Initial observation and interaction yields positive results as the ants accept people as a dominant form of life. However, the culture of the ants begins to change and they become intolerant of human presence. Not wanting to disturb the colonies they make observations at a distance whenever possible. To better understand the biology and interactions between species, they are forced to collect samples from time to time for analysis. Knowing full well that the ants will not accept humans, the researchers devise a remote control robot that has no sent and blends in with the environment so that is can enter and observe the ant colony unnoticed. And it does. Fiber optic cameras and sensitive recording devices send back data to help the researchers understand, and in the end, protect the newly found species.
I think you understand the parallel structure in that we are the ants and the island is earth. I think alien life is much closer then most people imagine. There is no doubt that alien life has noticed the television, radio, and other communications we have flying all over the planet. I believe they are smart enough to encode our languages and learn a great deal about us from it. In the same way, I think aliens could be connected to the World Wide Web, especially if they could obtain a sample computer and reverse engineer it (don't worry though, they still have to wait when the call tec support.). Seriously thought, if you use your imagination, you can see how a dominant form of life could infiltrate our information systems and find out more about us.
Any what about that robot the researchers sent in? Is there something foreign among us that collects data for alien species? I say there is. It may take the form of something we use every day, or it may mimic an animal or even a person. I think a person would be a good choice, as they would get the highest exposure. Only because of its superior design will people be just as ignorant about its presence as the ants are with the robot. But dose the robot harm the ants? It is designed and built specifically to be unnoticed and harmless, just as the alien probes are to people.
We will never be able to tell if there is an alien sitting right next to us on the buss, or tell if this thread was actually started by aliens wanting to know what we know about them. I believe aliens protect us as the researchers protect the rare and delicate species of ants. In the thread of a catastrophic asteroid collision, perhaps it will be the aliens that save us. But then again, we would never know about it.
So don't try to communicate with aliens, chances are, you may have already. If you are trying to get any sort of response, that is something you and the world may not be ready for. And they know it. Alien sightings often result in them being shot at, chased, or other such action. Some day, when humans are ready, humans and aliens will unite and their presence will be undeniable. But that is a long way off.