1st Q - Not really. Most of my friends listened to alt rock, one was a big metal head (Though now quite open to genre) and another one, who pretty much listens to what I listen to. The people who post **** on blogs influence me the most I guess. My bro did get me into listening to Phil COllins for a while in my early teens. Same with some rap. We shared a room so I didn't really have a choice, not being a music afficianado until pretty recently.
2nd Q - Maybe not specifically when it comes to albums, but genre, wouldn't have been held back probably
3rd Q - See: Bulldog, re: Dead Can Dance
A mate who ended up liking a lot of stuff similar to me.