an important consideration would be that if there is a highly intelligent extraterrestial life form that discovers our existence, would they even choose to reveal themselves to us? it would have dramatic consequences either way. for one thing; the human ego is not really good at accepting something that is absolutely more advanced then we are. i'd see us exploiting every possible avenue in order to make sure that that situation does not persist. would an advanced alien race want to get intermingled in that struggle for power? note that this would not have to mean all-out war, but the struggle will be there regardless, and very much determining and influencing our development. i don't think any intelligent race would reveal themselves to us unless we are more or less on par in terms of access and manipulation of certain categories in energy sources. i'd think that could be a general rule in some galactic code, to guarantee and preserve a species' own evolutionary autonomy in that fashion.