Since March of this year I've been running a private web spider looking at the number of web tags on web pages belonging to the Fortune 1000 and the top 1,000 web sites by traffic. Using the spider I've been able to see which products are deployed where, and how those products are growing or shrinking.
The web tags being tracked are those used for ad serving, web analytics, A/B testing, audience measurement and similar.
The spider captures everything about the page, including screen shots, and I'm able to drill in to see the state of a page and all its includes at the time of spidering. Here's shot of Apple with all the detail that the spider keeps.
The first interesting thing is to look at the top 1,000 web sites by traffic and see how many different tags are deployed per page. The average is 2.21, but if you exclude those that have no tags at all then the average is 3.10. Here's the distribution of number of tags against percentage of sites.
And of course, it's possible to see the market share of various different products. Here are the top 10 that I am tracking. Google Analytics has an impressive 43% of the top 1,000 web sites by traffic.
Since I've been tracking over time it's also possible to watch the growth (and decline). Here's the growth in the average number of tags on a web page (excluding pages that have no tags) since March 2009.
Finally, you might be asking yourself which site had 16 different tags on it. The winner is the celebrity gossip site TMZ.