It’s not illegal to share a metrocard. It’s stupid and annoying to do it on the sly like you are going to get in trouble, but it’s perfectly legal dude. The violation is if you fail to pay the proper fare. ie pay someone less to swipe you in or bribe the MTA employee to let you in. I’ve personally had a full on conversation with MTA Police while waiting the 18 minutes for a monthly metro card to reset itself. They asked me why I was waiting and told them outright. They didn’t tell me it was illegal, instead they opened the door for me and said “go right in.” Get over it you uptight fool.
Going With Eddie 
It’s not illegal to share a metrocard. It’s stupid and annoying to do it on the sly like you are going to get in trouble, but it’s perfectly legal dude. The violation is if you fail to pay the proper fare. ie pay someone less to swipe you in or bribe the MTA employee to let you in. I’ve personally had a full on conversation with MTA Police while waiting the 18 minutes for a monthly metro card to reset itself. They asked me why I was waiting and told them outright. They didn’t tell me it was illegal, instead they opened the door for me and said “go right in.” Get over it you uptight fool.