This has always been a beef of mine, opening a cache to find a dozen old and moldy calling cards. I understand why some people do it, they think it is cool and others like to read the cards or they just want to open the cache, toss in a card and keep moving as fast as possible. I don’t think anyone takes the time to read them or log books any more because there are so many caches and not enough time to find them all 
It is very rare to find a regular to large cache anymore and cachers no longer have pride in taking the time to write a nice note in the log book and I am guilty of that. When I first started geocaching I would leaf through the log book and see who found it and what they had to say and I would write a short thank you as well, but for the past 5 years or so, when the power trails started to show up and people’s numbers started to rise, the art of the “nice log in the cache” died and was replaced with the longer online log.
I like to open a cache and find a personal token left by some one, like a wooden nickel, poker chip, pathtag or any other homemade piece but the paper calling card is just clutter and adds to the mess inside of the container as the cache ages and perhaps gets wet and moldy. No one ever takes them out like a trade able item so the just keep piling up. I have removed them in the past to help keep a good cache clean if the container is filling up. I also remember a calling card causing some ”FTF confusion” in one of my caches because of a calling card being tossed in and the next person not looking at the contents of the container all that closely and found a clean log sheet to claim the FTF but don’t get me started on FTFs and the grief they can cause.
So now I have a few questions:
Do you take the time to read the log book and look at the calling cards?
Do you use calling cards and if so why?
Do you think they make the caches “messy”?
Do you think placing a card inside a container meets the requirement of ”signing the log book/sheet”?