This is common practice, but I've never heard of people getting upset about this. Why?
Well for one thing, a huge number of users on the Internet have dynamically generated IP addresses, so that sort of tracking isn't nearly as specific, or as useful, as keying in on someone's hardware. Without a good deal of dedicated IP addresses, and with more firewalls popping up on the 'net (obscuring people's true IP addresses in the process), IMO IP address data is only truly useful re: extremely general data collection.
This isn't to say that I'm extremely pleased at all the tracking going on using IP addresses, but its definitely more palatable than what these guys are doing. Who really needs to cross-reference with someone's real name and address? All they really want are your trends on the Web to know where you're going. They'll extrapolate most of your other characteristics on their own eventually.
Slashdot Mirror
Well for one thing, a huge number of users on the Internet have dynamically generated IP addresses, so that sort of tracking isn't nearly as specific, or as useful, as keying in on someone's hardware. Without a good deal of dedicated IP addresses, and with more firewalls popping up on the 'net (obscuring people's true IP addresses in the process), IMO IP address data is only truly useful re: extremely general data collection.
This isn't to say that I'm extremely pleased at all the tracking going on using IP addresses, but its definitely more palatable than what these guys are doing. Who really needs to cross-reference with someone's real name and address? All they really want are your trends on the Web to know where you're going. They'll extrapolate most of your other characteristics on their own eventually.