>> I wonder if being on Facebook reduces your motivation to build new friendships (it does take some work) since it allows you (with little effort) to maintain some form of very limited remote relationship?
As someone who moved away from my home country about 8 years ago and is still in touch with old friends via WhatsApp on an almost daily basis, this (regretfully) definitely rings true.
See, I'm the opposite. I moved away from my home country a little over 6 years ago.
Facebook meant I wasn't quite as lonely as I might otherwise have been. I've never had many friends where I lived anyway, but as it works out... I do now. Facebook has helped facilitate that and facilitate communication with the local friends.
Regarding keeping/losing old friends, I always believed that making new friends (and losing some of the old ones) is vital to someone's progress. Especially in a world that people relocate. I read this nice article about this here: