Discovering duplicate clicks

[#1]

Hi, I am trying to confirm my understanding on how I am being charged for CPC ads.  Please confirm that I can use the following fields to see if I am experiencing bogus click activity:

In my weblogs I am pulling out activity that has the gclid parameter appended to a landing page.  I see the following activity:

datetime                            ipaddress        url

2013-05-24 23:46:05.000    66.147.111.10  http://www.widgets.com/showproduct.aspx?productid=28&gclid=CLypn52zsbECFUff4AoddW0AmA

2013-05-24 23:46:05.000    66.147.111.10  http://www.widgets.com/showproduct.aspx?productid=28&gclid=CP6drp2zsbECFUff4AoddW0AmA

The only difference between these two entries is the gclid parameter; my understanding is that the gclid parameter is generated in adwords by selecting the autotagging box so that you can track your Google AdWord campaign's performance.    

Am I being charged twice for the same click here?  Or, am I missing something?  

thank you 

[#2 · Accepted solution]

You may well be paying twice for the same visitor - clicking twice.

There are reasons this happens - and not all are shady - often people will click on your ad - go back, click on someone esle's and then go back and click on your ad again....

Of course, competitors do sometimes click on our ads to use up our budget, or just to be an annoyance, but Google generally spots those invalid clicks and compensates the account.

[#3]

Hi stickleback.  Thanks for your reply.

Ok, the gclid param triggers the CPC charge; is that correct then? 

So if I see the same ip address landing on the same page at the same time (to the millisecond) then what does this indicate? 

I am guessing it would take the same user at least a second to go back and click on the same ad.  Is this some sort of automated program ?  Or am I missing something major.  E.g., is a gclid generated for every click the user makes once on my site and the first click, the one that brought them to the landing page is the only one that i get charged for? 

I can't imagine a real person being able to click that fast!  Thanks