I'm not sure I'd like to have advanced aliens landing here even if they are friendly. Consider what has happened to more primative cultures, right here on Earth, when confronted with a more advanced culture. Usually the more primative culture is damaged or destroyed.
American Indian vs European or the Zulus. Borneo cultures or the amazon cultures in more modern times.
SO I say to any alien culture studying us: Go ahead and study us covertly, but leave us alone to develop to at least interstellar capability.
And this a little OT: to those that say we have a wrecked spaceship at Roswell - SO WHAT? Even if true, it would be like a caveman finding a wrecked automobile. What would he do with it? He certianly couldn't fix it or build a new one! The most he could do, perhaps, would to get the principle of the wheel from it. And even that wouldn't be particually useful to a CAVEMAN!
