> 2. Chances of a hash collision on IP address is pretty small (i.e. statistically insignificant)
The problem, as I understand GP, is not so much the fear that two different IPs might collide. The problem is that seeing the same hash, you know that it refers to the same IP, and as such you can correlate users/sites over time (a privacy invasion).
That makes sense, kinda. Though I'm a little unsure why correlating http requests over an hour is not invading privacy, but doing the same over a week is?
The problem, as I understand GP, is not so much the fear that two different IPs might collide. The problem is that seeing the same hash, you know that it refers to the same IP, and as such you can correlate users/sites over time (a privacy invasion).