I noticed on ebay that some sellers hide the PSA cert number on their cards while others don’t. I just wanted to know what benefits/drawbacks existed of having this number publicly displayed. If you sell things or just display your cards online, I would like to know whether or not you hide this number and why, thanks 
I only hide the number when I am using a stock photo (from my own collection) of a card I have numerous copies of. Therefore I can sell 4 with the same picture instead of taking 4 individual scans. Otherwise I have no problem showing the cert #. And I always make the true cert number available at request. Hope that helps.
Ah okay, that makes a lot of sense. I thought it might be based on problems like people falsely claiming to have a card you own, but I guess if you have duplicates to sell it does make it more efficient to reuse a scan.
It’s not as bad with graded trading cards but with graded coins, there were instances where counterfeit coins were sold off using authentic cert numbers taken from eBay listings.