more on friends

do you have people that come in and out of your life in a constantly questionable presence? or is this just me?
this has happened often in my life, but at this posting i am speaking of a specific situation. the problem with these people is that one is (i.e., i am) never quite certain if they mean to be friends with you or not.
they seem happy to hear from you when you look them up.
they say they are glad you did look them up.
they even stay in contact for a few exchanges.

and then wham.

silence.

i truly do not understand this. yet to complain about it makes one appear...well, pathetic, needy, loser-like. but at the same time, one does not go through the trouble to get back in touch with people they've lost along the way without planning to keep things up this time around.

therein lies the rub.

what's a girl to do?