Google AdWords Click ID appearing in SERPs

How on earth did that happen?

[jsaipe]

In the Google SERPs, I noticed one of our page URLs has the Google AdWords click ID added to the end of the URL as follows:

www.[domain].com/training-courses/pay-per-click-marketing.php?gclid=COqu94uY-ZMCFRqH1Qody1gYVA

We've also spotted the same URL without the Google click ID in SERPs.

Firstly, I'm wondering how on earth did a URL with a Google click ID get indexed by Google?

Secondly, (which I've raised with Google AdWords), I sincerely hope we aren't being charged for clicks on this link?

Thirdly, if both URLs (with and without the click id) are in SERPs, how come the duplicate content filter hasn't kicked in as they both have the same metadata, page content and URL (all bar the click id).

Anyone seen this before?

PS: I am posting this to the Google Search forum as well.

[anallawalla]

I have seen this on their large publishers sites who get their AdSense data as an XML feed and not as JavaScript. This creates a crawlable ad. As far as I know this tag is used once, so someone clicking it in Google Search "should not" register as a paid click within AdWords.

A more common situation is that someone clicked your ad and then bookmarked the address which will include the gclid.

[jsaipe]

Yes the latter sounds the most likely contender.

You'd think Google would be able to remove their own AdWords click tags from their own index!?

I'm wondering whether to ask for an index exclusion on that URL via Google Webmaster tools, but I'm also concerned that Google might exclude the proper URL without the click tag.