That is true, but someone is already running it as a service on the blockchain itself. See:

https://www.proofofexistence.com/

You can imagine similar  services cropping up for things like torrents, sending btc tweets, etc. While I am not saying these things are particularly refined ideas in and of themselves, people should have an opportunity to play with them, and better testnet. 

Sent from my iPhone

On Jun 15, 2013, at 3:57 AM, "Luke-Jr" <luke@dashjr.org> wrote:

Timestamping ("proof of existence") doesn't need a coin at all. Just collect
all the hashes you need timestamped into a PoE merkle tree and add that to the
merged mining MT. It's pretty simple and straightforward, just needs someone
to implement it.

On Saturday, June 15, 2013 12:09:09 AM Dennison Bertram wrote:
Have your seen 'proof of existence'? It's basically a bitcoin notary
service that proves a document existed before it gets inserted into the
blockchain. While a good idea- you could argue that it's blockchain spam
as well- especially if one were to adapt it to high volumes in the future
for notarizing permanently things like tweets (for example) or combining
it with something like colored coins. These are great ideas, but maybe
better suited to a proto bitcoin without needing to fashion a brand new
coin.