Any item acquired at an event will hold significance to the person who acquires it, but some pieces of merchandise can be designed to have maximum resonance with their personal experience. In addition to displaying the company's information, they can become signifiers of what produced that specific piece and where it was handed out. Take promotional key chains, for example. Their portable nature and adaptability make them well suited to letting others know where they've been and who they've interacted with. While this might seem like a way to leave others "out of the loop," it's actually an enticement, and a method of drawing specific connections to a time and place that is very real for people.
What may escape the designers of promotional merchandise is how much power they have to connect their pieces to particular things. Personalized key tags that have both an identifier of the company and some particular link to where the item was distributed puts the owner of that tag in a select group, one that can be a signal to others and a conversation starter of sorts. Also, something as easily attached to things as a keychain can put a variety of other personal belongings into the same category. Friends and acquaintances that see a backpack with such an attachment, for example, can start asking questions about its origin, and eventually be drawn into the history of that customer's relationship with that accessory and where it came from.
Ultimately, including information about times and places can help distinguish custom key tags over over other, more disposable pieces. Companies should consider putting the name of an event, location or even an image that can help associate the key tag with some part of reality, rather than having just a logo. Remember, customers can find logos in other places. A certain year or convention name makes the item a little more special.