Yes, I've blogged about them before.
I just had a call from an agent wanting to show one of my listings. I took his contact information, and then asked - when do you want to show it? The response: "I'm here now and I can't get in." Since the owner was away, it was ok to show without notice and I gave him the code.
Then he asked, "Why do you use this code anyway? I've never seen one of those before." I wanted to say - "Just because of people like you, who don't make appointment and just show up at someone's door and try to get in!" But, of course, in one of my gracious moments, I didn't. I don't want to make him feel bad, or angry - I want him to sell my listing. So I explained why some sellers will allow a lockbox if it's coded, so they know in advance when it's going to be shown, rather than require me to meet an agent there. It's there for his convenience.
I listed a waterfront home this afternoon, and the seller is allowing a code protected lockbox. This seller, an engineer, asked if the code stayed the same - i.e., could the agent get back in another day with the same code, without an appointment. I told him that if the code wasn't changed, then yes, that was possible. Since he didn't like that, I agreed to change the code (I pass the house twice every day, going between home and office) after each showing.

I had someone call me the other day and tell me the key wouldn't work. Now I am a small office and I know when a listing is showing so asked did you call for an appointment? Well no but it is empty, well my showing instructions say to call for an apointment. You sould have told him not to try to go in your listings without calling first. That is a safety issue for your clients.
Some of these people are just "a bit slow" and really don't get it. They see the words electronic lockbox or see that pretty blue box on the front door and they think it's ok for them to just let themselves right on in.
Umm....hello? Did you read or see anywhere where it said, feel free to let yourself in? Didn't think so!
Jeff - it's unfortunate that so many agents don't even look up the showing instructions. They just go to the house. Yes, it's a safety issue. Most clients are more worried about people coming in when they ARE at home than when they aren't - i.e., they are taking a shower, don't hear the doorbell, and the next thing you know....
Becky - it's especially frustrating when our name and number are on the sign. I fully understand that they may be driving by when the client likes how it looks and wants to see it right away. If they haven't made an appointment, and they don't have a laptop or smartphone to look up the listing instructions, at least call the number on the sign.
Often it's an alarm they would set off if they entered without an appointment. It's not only annoying, it costs the seller money for each false alarm.
Renee - in our MLS you have to choose at least one in the showing category- i.e. Appointment Only. I don't know that there's any rule that you must also say lockbox if there is one.
Many agents in our area are checking CBS lockbox and then when you call, it doesn't have a code at all, they just wanted you to make an appointment. Hmmmm.