it's a webmaster tool to track users on a site. see this thread by Khai over at Daz : http://forum.daz3d.com/viewtopic.php?t=61541&highlight=

to quote :

*seems a script that allows the webmaster (and Google) to see what a user is doing on a site is loaded.

not that bad (aside from the report back)

but the slow down is caused by how it's used. each time we refresh or load a site the script is called from the Google servers.

now, on Daz alone, that is what, 300 calls a minute, at least? and thats just 1 site. now, imagine just how many sites use this service. (I know of at least 50 I've found since I started looking...)

the slowdown comes when you have god knows how many users (from estimates I've found say from a few hundred thousand to several million) all having the script sent from the google servers... a second. can we say bottleneck?

now for the user on a personal level? it means every site that uses this GA will be slowed down constantly... and since it seems more and more sites are using it... (for example alone, it's used by : Daz, Rendo, CP....)*