Someone who is noncommittal or agrees to everything but then never shows up and therein flaky. So flaky to the point of being almost professional in the practice of it. A professional flaky person. Hence, flake-up artist.
e.g.
Ben: "Liv! We haven't met up in ages!! Fancy meeting up this weekend? I'll be in your neck of the woods any how so we should deffo meet up for a crafty drink! You down?"
Liv: OMG! Ben!!! YES. We gotta do this! Bell me when your here and I'll come down!
(24 Hours passes and Ben arrives at agreed location)
Ben: "Hey Liv, I've just arrived! Where abouts are you?
A break up, but not truly a break up, i.e. both parties still feel an obligation towards one another, engage in frequent phone calls and "meetings", and feel guilty about beginning to date other people. It is a psychological way of coping with the difficulties of a relationship by both parties distancing themselves from the relationship itself and allowing one another breathing room.
Person 1: Hey, I justsawLeland and Lisa together last night. Didn't they break up because of school commitments?