I'll always greet whomever I'm seated next to. As for further conversation, although I enjoy talking with people I generally let my seatmate make the first move. I realize that many people are worried about the nonstop talker and may not want to initiate conversation. I've had some great conversations with seatmates on flights but at the same time, I've quite enjoyed those occasions where little is said and I get a couple hundred pages read or some sleep. I'm easy on this. I'm never too busy to chat but I'll always let my seatmate make the first move.