This can be accomplished through the following steps:
  1. Go to Communities > Special Events > Friends Asking Friends > Kintera Thon
  2. Mouse over the event and click on Reports
  3. Choose People: All Participants from the dropdown and click Run Report
  4. Choose Family Name from the Group 1 Drop down under Customize Report
  5. Choose Not Equal from the middle dropdown
  6. Leave the right field blank
    Once in place, things should look, as follows:
     
  7. Click Next
  8. Place a Check next to "Family Name" (bottom row)
  9. Click Finish
  10. Choose "No - Run the report immediately and wait for it to complete." and click Run Report