I like the aethereum project and suggest the snapshot of the blockchain to be anounced a few days in advance.
Why?
Lot of people have coins on exchanges etc. Some people would want to be able to move their coins to their own private keys
Also, will you need the private keys or is signing a standard message enough?
If it's the former, Trezor owners would need to move their coins out of their device before the snapshot, and import them after the snapshot.
(unless they want to expose their seed after the snapshot and then move their coins to a new seed; this isn't a good idea, because some people reuse some addresses or want to be able to sign with some addresses associated with their previous seed)
edit: I've read the FAQ, I'm like what I read

12. How exactly will I claim my æther?
Using your æthereum client, you can create one or several accounts. Each account has an associated address. To claim your æther, simply sign the æthereum address that you want credited with a bitcoin private key. Paste the signature into the claim aether window in your client and post the transaction to the network. This will provide cryptographic proof to the æthereum network of your right to claim your portion of æther from the nucleus.
13. But I dont trust you with my bitcoin private keys.
There is no need to trust us. Simply sign an æther address under your control with a bitcoin private key using whatever wallet you are comfortable with (e.g., blockchain.info, Armory, etc.,) and paste the resulting signature into the æthereum client.
So, the only thing to be decided is when to take the snapshot.