At the left you can see a screen shot of CW Skimmer at K8RRT's QTH. He was decoding the pileup for 5JØR, San Andres & Providencia, who was transmitting on 18.074 MHz. It turns out that K9W, Wake Island, was also operational at the same time but the K9W station was not on 17-M at this particular time. K9W's stated transmit frequency on 17-M is 18.079 MHz. That would be square in the middle of the pileup on 5JØR! (Click on any picture to see a larger image.)
On the right you can see the list of stations who were calling 5JØR, and who were being decoded by Tim's CW Skimmer program. Who knows how many others were calling that Tim was not able to copy? You can not see all the stations that CW Skimmer was decoding (see the extra yellow dots with no lines coming from them at the top of the image on the right) because Tim's monitor is not tall enough!
One interesting note is that while I was writing this Post, I was listening to 5JØR on 17-M. By my count, he made 20 QSO's between the times when he sent his own call. I looked at the clock when he made that second transmission of his callsign and then noted the time when he ID'd the next time. 12 minutes passed between those ID's! Considering the potential for confusion on which station you worked when there are multiple DX'peditions on the air at the same time (and similar transmit frequencies), it would be better if ALL DX'peditions gave their calls more often.