Earlier quoted context omitted.
From a rational standpoint, I generally subscribe to the selection bias you (and Scriptor in a separate reply) raise as #1. However, for the sake of discussion, let's operate under the assumption these sightings are legitimate/noteworthy. Personally, I grew out of bothering ant hills when I was about twelve. Nowadays, I pleasantly observe from high above. So why wouldn't aliens do the same? In this case, your second…
> one would assume some species capable of this technology would also have cultural norms about not interfering with less developed groups I would assume nothing of the sort. It's not as if humans even really conform to that norm. It's a pretty recent trend, at best. With aliens of unknown evolution/history, all bets are off.
For example, my hippie confidence does nothing to explain the likes of the Zerg or Tyranids, that's for sure. :)