Over at ClickZ the other day, an article by Rebecca Lieb mused on the web measurement possibilities inherent in Google’s Browser Sync.

As its name suggests, Browser Sync is a Firefox extension that lets you maintain bookmarks, history, saved passwords etc. across multiple computers—say home and work—provided you’re logged into your Google account on each machine. It provides obvious conveniences and seems to have been created by Google with the user’s interest in mind.

Lieb points out Browser Sync’s potential to improve online tracking for those who make this their business– web analytics providers and online advertising networks, for example:

“…No matter how many work, home, or other computers you regularly or sporadically use, if you use Firefox, have this extension installed, and are logged in, you can theoretically be counted as a single user insofar as any tracking application is concerned. That, in turn, would inform recency and frequency metrics. The implications are profound — and potentially a real breakthrough for analytics vendors and ad-tracking services. They stretch into Web analytics, anonymous behavioral targeting, affiliate marketing, accurate counting of unique site visitors, and likely a few more issues.”

While she marvels at this potential for increased precision, Lieb wonders if it will ever attain critical mass. Her conversation with web analytics gurus Avinash Kaushik and Eric Petersen reach similar conclusions: an overt embrace by analytics vendors is unlikely for reasons of positioning while the typical online user may have privacy concerns or simply remain indifferent. Kaushik comments that as people interested enough an esoteric plug-in to discuss it, let alone install it he and Lieb “live in a rarefied world.”

Though installation is only mentioned in passing, it is, of course a key hurdle. Lieb’s article leads with “If you’re one of the burgeoning number of Firefox users, you probably also use a number of the many extensions available to stretch, modify, personalize, and customize the browser’s capabilities.”

That may be optimistic. While those who use Firefox extensions often assume that no one could resist them, I’ve seen some sources suggest that as few as 10% of Firefox users install any extensions (a definitive stat is elusive.)

I think of Browser-Synch as roughly analagous to an Advanced Feature on a website - some folks may benefit from it, but most will do just fine without it, are unlikely to go looking for it, and may get annoyed if overemphasis presses its adoption.

But what about the Advanced Feature that’s available by default and may even be enabled unbeknownst to you? As Kaushik points out, the code for Browser Sync was written in open source– there’s nothing to stop Microsoft from including it in the next version of Internet Explorer. Certainly that would accelerate the install rate, but what would it do to “choice-bloat” and the real quality of the IE experience? The question of how to implement a feature of benefit to some but interest to few will always spark debate.