Each time I compose a reply to the Plane Down in Hudson River - NYC thread in R&N I am informed that I have already 'pinged':-

* YouTube - P&W-F100-220C Engine Stall (http://www.youtube.com/watch?v=mQNUrYoFM2E)
* http://www.msnbc.msn.com/id/28681048/displaymode/1...

(under the 'Send Trackbacks to)

Is this something that I can cancel?

It probably means that those other pages linked to that discussion, sending a "trackback (http://en.wikipedia.org/wiki/Trackback)" in the process. These things are flying around the Internet all the time - nothing sinister.

G-CPTN - some info here: http://www.pprune.org/computer-internet-issues-troubleshooting/334118-permalinks-linkbacks-trackbacks.html