The id is currently stored into the file
..Chrome\User Data

under section: user_experience_metrics - 
client_id

This is by design, not a bug.

The user_experience_metrics ID cannot be generic. We need a different ID for each 
instance of the program so that statistics about one event (crashes, eg) can be 
correlated with other events (number of page loads).

I'm not sure why you'd want to change this.

Maybe you're just asking how you can turn it off/prevent Google Chrome from using it?
If so, open the Wrench menu > Options > Under the hood and uncheck "Help make Google 
Chrome better".

There's a little confusion here that I'd like to clear up. There are two IDs being 
discussed. They are stored and used separately.

First of all, there is an installation ID (iid) which is created at install time to 
de-dup install counts. This is necessary to accurately count the number of successful 
installations that have occurred.  The iid is generated randomly (not based on any 
other information) and is deleted in the next update check after first run. 

There is a second ID called the clientID which is used for the user metrics service. 
This is an opt-in service that lets users send usage statistics to Google so that we 
can learn how the product is being used for the sake of making improvements. It helps 
us answer questions like, "Are people using the back button?" and "How common is it 
that people click the back button repeatedly?" Users can always update their 
preference about sending usage statistics on the "Under the Hood" tab of options.

ok - thanks for clarify this.
There is a similar new function in eclipse ganymede called "Usage Data Collector".
Eclipse asks each time before sending data and also it generates a log file where I
(the user) can see which data will be send to eclipse foundation. 
Can I see also the informations send out by chrome?
Would not be a similar control dialog meaningful for chrome to inform the user how
google will treat the data provided by individuals?