[simonw]

10 or 20 years ago there wasn't nearly as much readily available data to be mined. Today even moderately high traffic sites generate GBs of log files a day, not to mention the enormous quantity of high value data available through various APIs.

[aaronblohowiak]

you don't actually need all of the traffic to make meaningful conclusions. Tracking a statistically sound random sampling of user sessions provides most of the benefit for pattern analysis uses.