Sally_Stitts - 10:00 pm on Jul 7, 2010 (gmt 0)

I had always left my GWT - Site Configuration - Target User In: Unlisted.

But then I became concerned about all the traffic I was getting from India, the Philippines, Singapore, Malaysia, and Pakistan.

So, on Feb, 15, 2010, I set my Site Configuration to -
Target Users In: United States. I compared my visitors in January, to my visitors in the month of June.

Here are the results -
United States - minus 0.5%
India - plus 0.3%
Philippines - plus 0.5%
Singapore - plus 0.1%
Malaysia - plus 0.1%
Pakistan - no change

Conclusion: Setting the Target Country to United States has no positive effect, at all, whatsoever.

At least I finally tried it. So all that previous advice about "Don't specify anything" seems to be verified, at least for me, for the US. I think this is just a "show" or "ego" parameter, much like Google Toolbar Page Rank. IMHO.