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.