First of all I believe that Alien beings have never travelled to earth. This I will base to the fact that travel between solar systems is nigh impossible to us. It will take many years for us even to build up our technology to fathom that we will reach OUR outer confines of the solar system, let alone travel to a new one within one lifetime. If we ever do come across any sort of intelligent life we will initiate contact immediately, because we have had to face many tribulations to get to that stage, and we are not going to stop within the last 10 meters of our marathon, to deliberate whether or not to say hello to the indiginous life on the newly discovered planet. Thus if an alien being did arrive to our planet, it would only be logical that it would want to establish contact immediately, and not start to beam up people into the mother ship to open them up and make our females pregnant with their hybrid offspring.
Lets say that they did come to earth (a waaaaay big longshot in my book anyway, but...),you would think that if they truly did want to take subterfuge close their hearts, they would be a little more inconspicuos wouldn't you? I mean frankly if I'm spying on you from a UFO I'd try and hide my presence a little, like for example mimicking an aeroplane's lights and cruising along at a similar speed, not start flashing all the colours in the fricking rainbow and then getting the hell out of there at the speed of light. These things invariably bring about unwanted attention which to any spying, or even scientific research at that would be compromised.
Scientifically if I were studying a pack of chimpanzees, I'd try and make my presence known as little as possible, so as to decrease the factor by which my presence in their environment is having an effect on their behaviour, this is known as good scientific protocol. However it seems that these alien beings are completely disregarding all basic scientific research laws, interfering with their 'supposed' scientific experiment by leaving them to be seen, and sticking probes in places which are nobody's business. I don't care from which point in the cosmos you belong to, but good science is good science everywhere, and if these alien beings are completely disregarding it, hell they must not be as clever as they are made out to be.
I'll let you guys think about this, and please post your feedback, I want to know how flawed my argument is!! I'll post my views tommorow about what "I" think abductions, and UFOs are (trust me, from my perspective it is far more sinister than you fathom!!! I don't think that people who have said that they are abuductees are lying, well not all of them!). I'm signing off for now, 'coz I gotta wash my shorts for tommorows physiotherapy practical and it is 15 past 1 in the morning here!!! In any case....