Person-Marks typically "disappear" when FORMER iHub Account-Holders let their iHub Contracts lapse, or when they CANCEL out of iHub altogether, or when they are BOOTED off iHub.
In all those cases, any-and-ALL Person-Marks that person granted are Removed from their iHub recipients, along with the departing individual.
Please anybody, please correct me or fine-tune my answer if it's not quite accurate!
...btw, One Replacement Person-Mark to you.
All the Best to Everybody and FEEL!$ :-)