In response to Tomte's criticism, this all boils down to the certification level http://tanguy.ortolo.eu/blog/article9/pgp-signature-infos
1) A fingerprint on a possibly compromised business card == 0
2) A fingerprint verified by phoning someone == 1
etc,
And associated with that independently is of course the level of trust.
Sorry Tomte for not replying immediately to your message, but I've posted too much on this apparently.
You are missing the part where it was suggested that the recipient of the business card telephones you and asks to verify the fingerprint.