Oh, OK, it's kind of interesting I guess. Still think the value of this data is more at a macro level than a personal level i.e. the person inputting it is basically doing data-entry for a group that will then sell the trends. hmmm.
... but we shall see.
anyway - that leads straight to the main flaw that there isn't enough incentive to checkin - therefore the trends are unreliable and the data less valuable.