"Hardly surprising, we all know Google respects privacy about as much as a hungry cow respects my lawn..."
While it's healthy to question the security of integrity of data-harvesting there's one major difference between Google and anyone else. Namely, Google is honest about it.
Also, they've never actually been caught doing anything untoward with the data which is quite impressive considering their size, mindshare and skepticism shown by people such as yourself.
So in the end we 'know' nothing but what we've actually seen or heard and judging Google by those merits they're probably the most stand-up company of their size anywhere.
On another note, for those wondering, payload data refers to what most would simply term 'data'. In other words the actual information transferred as opposed to header data that only contain the source and destination of the data, it's type, length and checksum etc.