the only reason we could think of for wanting unique visitors was for the marketing people or investors/stakeholders/shareholders. Parsing the request logs should be sufficient for every other metric.

We had a bunch of meetings about this at what essentially amounted to a giant information superhighway billboard company. IIRC someone brought up using cache headers even back then, because it didn't require cookies or javascript, which we couldn't guarantee would be "up to date", this is back in "target IE6, still" days.

As one of my networking friends said, advertisers usually know everything about your metrics, even if you don't. You can't really fudge the numbers in your favor, so raw requests or QPS or whatever ancillary metric would be enough.

the method in the article is defeated by clearing your session when you're done browsing, or using incognito/private browsing tab, as that should mark all "cached" items for deletion.