For
It funds free services and causes no direct harm.
Against
Data can still be traced back and misused.
Anonymous excerpts, translated where noted.
“it is not your specific data and couldn't be traced back to a single person”
“Massive data repositories can reveal trends that teach medical researchers about disease”
“Anonymized doesn't always mean that your data isn't still tied to your name/account/etc.”
“Once sold: You usually can’t take it back”