It appears ComScore is working on metrics to measure AJAX and Flash according to an article in ARSTECHNICA yesterday.  According to the article:

"…..While page views will not altogether cease to be a relevant measure of a site's value, it's clear that there is an increasing need to consider page views alongside newer, more relevant measures. comScore is proud to continue carrying the torch as an industry innovator with the development of a new suite of metrics that will effectively address the Web 2.0 landscape by including enhanced measures of user engagement and advertising exposure. We will be introducing these new metrics to the industry in 2007."

"……If comScore says you have 1 million readers and 3 million page views, but you know that you have 2 million readers and plenty of interactivity not reflected by page views, it can cost your website money. Advertisers might look down their nose at you. Companies may chose to ignore you. Generally speaking, you're not getting credit for your traffic. This hurts some more than others."

I'm sure MySpace is in no hurry to have the ComScore's metrics be updated for Web 2.0 since it, and many other top media sites, get credited with the current metrics for inflating pageviews from inefficient coding and site design that don't actually reflect more interest in the site by their visitors.  The ComScore article goes on to say…

"…To make matters worse, many of these traffic measurement services use data collection methods which are known to undervalue certain classes of users, including those dedicated to technology. ComScore, for instance, tracks users who voluntarily participate in an e-commerce tracking system, and then it uses behavioral data from those opt-in users to extrapolate trends on a massive scale. As you might guess, this means that some sites are under represented. Ars Technica, for instance, attracts highly savvy readers who by and large do not opt-in to such systems. The same is true for most technology sites online, and their scores suffer; comScore does not truly know our audience, only a small portion of it. Other metrics might rely on a toolbar or similar opt-in systems, which immediately raises the question of what qualifies as a "standard" Internet user. If that definition remains "guy who buys things online using Internet Explorer with this special toolbar installed," then you can see the problem.  "

I would think that 2007 will become a watershed year for Audience Measurement - what ComScore does the other measurement services will have to eventually match if they want to stay relevant much of the web is using Flash and Ajax.

"…Television has Nielsen, but the web has no clear leader for ranking the world's busiest websites. There's no shortage of competitors in the space, of course, and you've probably heard of many of them: Alexa, comScore, HitWise, and the newcomer, Compete. None of them provide uncontested results, however. Many of them do worship the almighty "page views" god, but that's about to change."

But it's hard to see how Compete and Alexa can change how and what they measure that radically…. they're free services and are picking up data from their toolbar.