My exBPDbf didn't and still doesn't have a FB account. Years ago he had one, but deleted it when his second ex-wife started asking about all the women he was friends with. FB would make it way too easy for someone to keep up with him (this from his own mouth). He likes to fly under the radar.
I think it's just up to the individual, like most things. Some pwBPD or BPD traits enjoy the narcissistic supply that FB can provide. For that matter, so do some 'normal' people. Plus it can be a convenient way to meet people, and potentially find new real-life supply. And yes, the distance probably helps some pwBPD by lessening the attachment. For the same reason, some pwBPD are drawn to long distance relationships.
FB can be obsessive on both sides after a breakup, too. I'm glad I didn't have to deal with the temptation to check out my ex's FB page after the breakup. Detaching and healing was difficult enough without that added into the mix.
