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I'm still testing my release I sent out in November. Some observations:

• Stable traffic of 10-15 visitors each day directly from the PR site where the release was done
• Incoming do-follow links from HIGHLY reputable newspapers (syndicated though, not reporters)
• Ranking increased for the two keywords included in the release

I did not see any negative effect ... yet.

If I do, I'll let you know.

Anyone else has done a test like that recently? Please share

That's a good one! One of my clients did that too on a regular basis. After we found the tag they got over 500 new pages ranking very high, and of course we were credited with the improvement, so that was a nice thank you check

How is this related to the question?