Recently, we've had more than one resident inquire about letting strangers into the building or garage. Here's the thing... we have a controlled access community, and you have the control!
If you don't personally know the individual who is wanting inside, you are under no obligation to let him or her into "your home." Let's assume someone you don't recognize meets you at the front door and says, "I left my key fob upstairs, but you know me... I live in unit 000." A great response is, "I am so sorry that I don't recognize you. You might want to call yourself on the intercom and let yourself inside." People seldom forget their cell phones and often forget this is an option.
If you're the one who has forgotten your fob (and your phone), please remember that the person who is refusing to let you into the building is simply protecting the community. There's no need to make someone feel bad, or accost them after the fact in the elevator. Would you let some stranger into your front door?
It is the same situation with the garage. People should be stopping and waiting for the door to close. Most of the time the car prowler or bike thief comes in right behind someone who chooses not to stop and wait.