Say you were at an UFC or a place that had a someone like Randy Couture or Oscar Delahoya there and got a pair of gloves signed.
Say you wanted to sell those gloves online.
How would you authenticate them so the buyer knows the signature is not fraudulant?
take a picture
http://www.psacard.com/submission_center.chtml
http://www.spenceloa.com/
For something like a glove, you would just get a certificate card: