Well one big reason I think is that some people collect a specific thing for a specific reason... and if it gets lumpped into this uncontrollable aggregate sum, it might not be useful to them.

Now, if there was a reliable way to get both EXACTLY what I just collected, and the aggregate overall, then maybe it would be more useful...

how about this for a compromise... have it always send the data to your mystic place, but ALSO give the user the option of specifying an additional place for it to go, so they can use it for personal things as they see fit...

I might be willing to make that concession, as long as everyone benefits from the information. My main goal is to share the information with the community and my only issue with having the information uploaded into the user's private database is that people will hoard the information for themselves and it will benefit noone.