It's really up to you, he's trading a 1:1 value (shipping aside), in my opinion this is a method of cold storage or, as you said, face-to-face trading. (Possibly not face-to-face, if the trades sole purpose was to hide the exchange of a large number of bitcoins, eg. dark net trade.)
If used for transferring bitcoin, it would be awesome if we could send money to the address on the coin. Why is only the first 8 digits on there?
Interesting idea and you just showed me that these are way cooler than I first thought!! In theory I can make one of these coins worth as much as I want to, right? I just can't make it worth less. This proves that these coins are, in fact, one way WALLETS - not just coins. All I have to do is:
Lookup the entire public key in the block chain.
Send more to that key.
Let's say I send 99 coins to the address. Wala! A 100 BTC coin.
I can then give the coin to someone and tell them it is really a 100 BTC coin.
They can verify my claim in the chain.
When they "crack it open" then can transfer all 100 BTC to their account (or wherever).
Also another very useful application is that you can give the coin to someone and then transfer more to it over time AFTER they have it, like give one to a nephew and then transfer more on each birthday - or whatever!
You can meet someone face to face once, give them a coin and from then on you can make payments to them and you know the payments are going to the intended destination, the bitcoin address you gave them!
It looks like these are a very cool way to store (and transfer) any amount of value "off line" - just like the paper wallet idea!
This.