The guidelines are devised, she said, from myriad internal experiments to gauge users' preferences.
Polyvore's most valuable asset is the intelligence that it gathers about its users' preferences.
The first engineer discussed a piece of software that studied users' preferences as they browsed the Web.
DVRs can even learn their users' preferences and record programmes accordingly, thus creating the equivalent of a personal TV channel.
Buyers can also pay for "drop checkers", which automatically monitor ticketing sites for new events and pick up tickets automatically based on the users' preferences.
The P3P software can detect and compare users' preferences for privacy protection with the policies on each Web site and warn them if they are in conflict.
Stoking envy among traditional television executives, the Web site collects a trove of data on its users' preferences in programming and ads.
Leaving advertising aside, cookies fill three major roles on the Guardian's own site, as GNM product manager Piers Jones explains: "Cookies do a great job at remembering users' preferences," he says.
Windows 8 will use the cloud to store users' preferences in the way they set up their computers – from home screen photos to the collection of apps or favourite websites.
Facebook's "data-base of affinity", as Elliott calls it, which is based on its users preferences, rather than intentions, has great potential for Facebook to power brand advertising, rather than direct response, he says.
Finally, Kapuer learns users preferences from scratch.
