I have to say, I am not a fan of the "calling cards" left in caches. I find that many of them are not high enough quality to be worthy of collecting and therefore they just take up space in the cache, collecting dust because nobody empties them. In some situations, it makes the cache-logging more difficult, trying to keep track of all sorts of different papers and make sure they all end up back in the cache. This is especially true in winter, when dealing with numb fingers.
I like the idea of collectible, signature items, such as MHz or Stuntman poker chips. Particularly if each one is particular, or there is a set, or there is some specific aim to the collection, rather than just simply collecting them.
I also have to say that I don't like signature items that are just random items (sorry, kingkev!). I don't mind them so much because they are just like trade items, however, they end up just creating clutter. I prefer items to be collectible, or interesting, or at least follow the theme of the cache.
As other cachers may have noticed, the Wagonmaker "calling card" is always signing the log in green ink. I really like this approach to leaving our mark because it is unique (I have yet to see another log in green ink) and doesn't take up any extra space in the cache. [This has also taken us through a number of green pens. First I broke one in half, then I lost one, then another cacher broke one in half... we're already on green pen #4!]
SO, all this to say that I'd be leary of creating more signature items, unless they were collectible and/or unique. I also think I'd have to see a specific idea or event before condemning or applauding it entirely.