Last time my browser started to be sometime unresponsive during browsing talk.maemo.org. I looked into HTML and found at the end of page this code:

And specifically at a moment google-analytics.com didn't response and that was a reason of my browser "hangs".

What is it? It was EXACTLY in my PRIVATE messages area!

You can check it by yourself - just go to firefox/mozilla "View/Page Source" and go to the end.

It's a way to get your credit card details...

Just kidding, a way of getting stats about who visits the website:
Where they are from (ip based)
Browser
Where they went etc.
Very useful for working out if a site is working well

Web site should warn about it. Without that warning there is an impression that "private" messages is private.

It doesn't snoop on the content of your messages, although I'm not entirely certain what information it does collect. At worst, most of these analytics companies would collect things like which page referred (e.g. linked) you to the page you're on, etc. Your private messages are still private.
If you still aren't comfortable with this (and I don't really blame you - Google is huge enough that some amount of healthy paranoia couldn't hurt), then you can install something like the NoScript addon for Firefox, which allows you to block scripts per domain. (So that anything from google-analytics.com would be blocked on any site.) I don't know if NoScript has blacklist functionality (normally it operates as a whitelist), but it will do the job nicely.

Addendum: As was mentioned, services like Google's are used all over the place to keep stats for webmasters. For example, if you write a blog, your provider might let you find out, for each day, how people found your blog (search terms, links, etc.), which outgoing links they clicked, and other details that are useful for finding out whether people care about your site, and what they do on it. For example, if I wrote a tutorial that ended up ranking high in search results for a commonly-confused query, and noticed lots of people accidentally browsing to it from a search engine, then I might put a note at the top mentioning that, and pointing to a better place. That's a lame example, but that's the gist, anyway.

for certain values of "private" GA does not read the contents of your private messages. Almost everything it does can be (and probably is being) done via server log analysis as well.

And the server admins can always access all data if they would feel so inclined.

Also the privacy policy (see footer) states that visitors may be tracked using cookies and by other means.

If you're worried about your privacy on the net I suggest disabling Flash and JavaScript first and enabling cookies only for sites your really need them on.

Surprise... google analitycs is on every 2nd page on interwebz.

Well, yeah, you make a fair point. Your correspondence isn't being datamined, but it may "leak" information to an analytics provider in indirect ways (e.g. outgoing links - just an example, I'm not sure). IN regards to Flash, though, it's not always practical to fully block it, but apart from a good dose of AdBlock and NoScript, you should also take a look at the suggestions in this Wikipedia article for dealing with other Flash-based privacy concerns.

Thanks, you just take me on ground - in past I always disabled Java/Javascript in browser but now I know why. I can't explain myself why I reverted my policy... may be Maemo influence...