I'd like to believe in friendly aliens, but I changed my expectations since I read "Collapse". I don't recall if there were in fact any friendly encounters, but for the most part I remember from the book that newly discovered human populations were destroyed by the explorers from other countries.

There is also at least one example of a pacifist society that was completely butchered when they were discovered by less pacifist people, even though they gave those people a friendly welcome.