Due to Etherchain resets once every while, it is important to note we now have 2 forks of chains.
One has about ~4000 blocks, the other 10,000+ blocks.
On my PC and on http://etherchain.org/
I see the longer chain.
But if the dev team wants to flush and really reset the chain, here is the procedure:
1. announce it in advance (transparency is important!)
2. release team (core developers) must generate a new genesis block
3. hard code the new genesis block hash into a new client, such as new BETA/POC or an actual release.
This way, the older (longer) chain will no longer over-ride the short chain.